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Document And Entity Information - shares	9 Months Ended
Document And Entity Information - shares	Sep. 30, 2018	Oct. 31, 2018
Entity information [Abstract]
Entity Registrant Name	EVERGY, INC.
Entity Central Index Key	0001711269
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		263,455,083
Entity Current Reporting Status	Yes

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 679.7	$ 3.4
Receivables, net	496.5	290.7
Accounts receivable pledged as collateral	195.0	0.0
Fuel inventory and supplies	520.9	293.6
Income taxes receivable	20.8	0.0
Regulatory assets	332.5	99.5
Prepaid expenses and other assets	73.6	39.8
Total Current Assets	2,319.0	727.0
PROPERTY, PLANT AND EQUIPMENT, NET	18,836.0	9,553.8
OTHER ASSETS:
Regulatory assets	1,518.1	685.4
Nuclear decommissioning trust fund	518.0	237.1
Goodwill	2,333.5	0.0
Other	379.7	244.8
Total Other Assets	4,749.3	1,167.3
TOTAL ASSETS	26,075.2	11,624.4
CURRENT LIABILITIES:
Current maturities of long-term debt	709.6	0.0
Notes payable and commercial paper	675.9	275.7
Collateralized note payable	195.0	0.0
Accounts payable	303.7	204.2
Accrued dividends	0.0	53.8
Accrued taxes	282.1	87.7
Accrued interest	119.6	72.7
Regulatory liabilities	117.2	11.6
Other	225.8	89.5
Total Current Liabilities	2,659.2	823.7
LONG-TERM LIABILITIES:
Long-term debt, net	6,639.8	3,687.6
Deferred income taxes	1,536.0	815.7
Unamortized investment tax credits	378.9	257.1
Regulatory liabilities	2,357.1	1,094.0
Pension and post-retirement liability	949.7	491.2
Asset retirement obligations	622.7	380.0
Other	231.9	133.3
Total Long-Term Liabilities	12,767.2	6,940.3
Commitments and Contingencies (Note 12)
Shareholders' Equity:
Common stock	9,236.4	2,734.8
Retained earnings	1,452.5	1,173.3
Shareholders' Equity	10,688.9	3,908.1
Noncontrolling Interests	(40.1)	(47.7)
Total Equity	10,648.8	3,860.4
TOTAL LIABILITIES AND EQUITY	26,075.2	11,624.4
Westar Energy Inc [Member]
CURRENT ASSETS:
Cash and cash equivalents	3.3	3.4
Receivables, net	347.5	290.7
Related party receivables	0.7	0.0
Fuel inventory and supplies	268.7	293.6
Regulatory assets	120.4	99.5
Prepaid expenses and other assets	31.9	39.8
Total Current Assets	772.5	727.0
PROPERTY, PLANT AND EQUIPMENT, NET	9,637.5	9,553.8
OTHER ASSETS:
Regulatory assets	693.7	685.4
Nuclear decommissioning trust fund	245.8	237.1
Other	227.3	244.8
Total Other Assets	1,166.8	1,167.3
TOTAL ASSETS	11,747.7	11,624.4
CURRENT LIABILITIES:
Current maturities of long-term debt	300.0	0.0
Notes payable and commercial paper	326.3	275.7
Accounts payable	135.1	204.2
Related party payables	73.9	0.0
Accrued dividends	0.0	53.8
Accrued taxes	144.9	87.7
Accrued interest	65.3	72.7
Regulatory liabilities	91.6	11.6
Other	109.4	89.5
Total Current Liabilities	1,276.8	823.7
LONG-TERM LIABILITIES:
Long-term debt, net	3,389.7	3,687.6
Deferred income taxes	787.1	815.7
Unamortized investment tax credits	255.1	257.1
Regulatory liabilities	1,136.9	1,094.0
Pension and post-retirement liability	465.2	491.2
Asset retirement obligations	257.8	380.0
Other	127.8	133.3
Total Long-Term Liabilities	6,470.7	6,940.3
Commitments and Contingencies (Note 12)
Shareholders' Equity:
Common stock	2,737.6	2,734.8
Retained earnings	1,302.7	1,173.3
Shareholders' Equity	4,040.3	3,908.1
Noncontrolling Interests	(40.1)	(47.7)
Total Equity	4,000.2	3,860.4
TOTAL LIABILITIES AND EQUITY	11,747.7	11,624.4
KCPL [Member]
CURRENT ASSETS:
Cash and cash equivalents	3.4	2.2
Receivables, net	102.9	106.3
Related party receivables	142.2	84.7
Accounts receivable pledged as collateral	130.0	130.0
Fuel inventory and supplies	183.8	197.0
Income taxes receivable	0.0	5.4
Regulatory assets	145.6	153.6
Prepaid expenses and other assets	35.7	27.6
Total Current Assets	743.6	706.8
PROPERTY, PLANT AND EQUIPMENT, NET	6,660.3	6,565.6
OTHER ASSETS:
Regulatory assets	479.5	545.1
Nuclear decommissioning trust fund	272.2	258.4
Other	54.5	48.0
Total Other Assets	806.2	851.5
TOTAL ASSETS	8,210.1	8,123.9
CURRENT LIABILITIES:
Current maturities of long-term debt	400.0	350.0
Notes payable and commercial paper	209.2	167.5
Collateralized note payable	130.0	130.0
Accounts payable	132.9	249.0
Related party payables	3.2	0.0
Accrued taxes	121.5	29.0
Accrued interest	39.5	32.4
Regulatory liabilities	15.3	8.3
Other	98.5	98.3
Total Current Liabilities	1,150.1	1,064.5
LONG-TERM LIABILITIES:
Long-term debt, net	2,129.9	2,232.2
Deferred income taxes	619.6	616.1
Unamortized investment tax credits	120.9	121.8
Regulatory liabilities	862.9	770.9
Pension and post-retirement liability	522.3	512.2
Asset retirement obligations	222.7	231.4
Other	80.7	61.6
Total Long-Term Liabilities	4,559.0	4,546.2
Commitments and Contingencies (Note 12)
Shareholders' Equity:
Common stock	1,563.1	1,563.1
Retained earnings	934.8	949.7
Accumulated other comprehensive income	3.1	0.4
Shareholders' Equity	2,501.0	2,513.2
Total Equity	2,501.0	2,513.2
TOTAL LIABILITIES AND EQUITY	8,210.1	8,123.9
Variable Interest Entities [Member]
CURRENT ASSETS:
PROPERTY, PLANT AND EQUIPMENT, NET	170.9	176.3
CURRENT LIABILITIES:
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.0	0.7
LONG-TERM LIABILITIES:
Long-term debt, net	51.1	81.4
Variable Interest Entities [Member] \| Westar Energy Inc [Member]
CURRENT ASSETS:
PROPERTY, PLANT AND EQUIPMENT, NET	170.9	176.3
CURRENT LIABILITIES:
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.0	0.7
LONG-TERM LIABILITIES:
Long-term debt, net	$ 51.1	$ 81.4

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Shareholder's equity
Common stock - shares authorized (in shares)	600,000,000	275,000,000
Common stock - par value (in dollars per share)	$ 0	$ 5
Common stock - shares issued (in shares)	264,797,584	142,094,275
Westar Energy Inc [Member]
Shareholder's equity
Common stock - shares authorized (in shares)	1,000	275,000,000
Common stock - par value (in dollars per share)	$ 0.01	$ 5
Common stock - shares issued (in shares)	1	142,094,275
KCPL [Member]
Shareholder's equity
Common stock - shares authorized (in shares)	1,000	1,000
Common stock - shares issued (in shares)	1	1

Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
OPERATING REVENUES	$ 1,582.5	$ 794.3	$ 3,076.1	$ 1,976.2
OPERATING EXPENSES:
Fuel and purchased power	383.7	189.8	748.9	415.4
SPP network transmission costs	58.4	62.6	194.4	185.0
Operating and maintenance	330.4	140.6	754.2	415.6
Depreciation and amortization	193.9	94.6	411.6	277.3
Taxes other than income tax	83.0	41.8	183.5	126.4
Total Operating Expenses	1,049.4	529.4	2,292.6	1,419.7
INCOME FROM OPERATIONS	533.1	264.9	783.5	556.5
OTHER INCOME (EXPENSE):
Investment earnings	4.9	1.0	6.2	3.5
Other income	1.6	3.9	5.3	5.7
Other expense	(30.8)	(11.5)	(55.2)	(29.6)
Total Other Income (Expense), Net	(24.3)	(6.6)	(43.7)	(20.4)
Interest expense	89.1	43.4	191.3	128.2
INCOME BEFORE INCOME TAXES	419.7	214.9	548.5	407.9
Income tax expense	64.1	55.8	28.3	112.6
Equity in earnings of equity method investees, net of income taxes	2.0	1.6	4.7	4.9
NET INCOME	357.6	160.7	524.9	300.2
Less: Net income attributable to noncontrolling interests	2.6	2.4	7.6	10.2
NET INCOME	$ 355.0	$ 158.3	$ 517.3	$ 290.0
Basic earnings per common share (in dollars per share)	$ 1.32	$ 1.11	$ 2.61	$ 2.03
Diluted earnings per common share (in dollars per share)	$ 1.32	$ 1.11	$ 2.61	$ 2.03
Average number of basic common shares outstanding (in shares)	268.6	142.5	197.9	142.5
Average number of diluted common shares outstanding (in shares)	268.8	142.5	198.0	142.5
Westar Energy Inc [Member]
OPERATING REVENUES	$ 764.8	$ 794.3	$ 2,015.9	$ 1,976.2
OPERATING EXPENSES:
Fuel and purchased power	169.7	189.8	463.2	415.4
SPP network transmission costs	58.4	62.6	194.4	185.0
Operating and maintenance	141.7	140.6	491.4	415.6
Depreciation and amortization	95.9	94.6	281.6	277.3
Taxes other than income tax	42.2	41.8	128.8	126.4
Total Operating Expenses	507.9	529.4	1,559.4	1,419.7
INCOME FROM OPERATIONS	256.9	264.9	456.5	556.5
OTHER INCOME (EXPENSE):
Investment earnings	0.0	1.0	(0.4)	3.5
Other income	1.3	3.9	4.9	5.7
Other expense	(15.2)	(11.5)	(36.1)	(29.6)
Total Other Income (Expense), Net	(13.9)	(6.6)	(31.6)	(20.4)
Interest expense	43.9	43.4	132.1	128.2
INCOME BEFORE INCOME TAXES	199.1	214.9	292.8	407.9
Income tax expense	22.4	55.8	(22.0)	112.6
Equity in earnings of equity method investees, net of income taxes	1.3	1.6	3.7	4.9
NET INCOME	178.0	160.7	318.5	300.2
Less: Net income attributable to noncontrolling interests	2.6	2.4	7.6	10.2
NET INCOME	175.4	158.3	310.9	290.0
KCPL [Member]
OPERATING REVENUES	559.6	595.7	1,408.9	1,474.3
OPERATING EXPENSES:
Fuel and purchased power	142.4	143.9	392.4	367.3
Operating and maintenance	127.3	114.3	354.5	350.7
Depreciation and amortization	71.9	66.3	209.0	199.9
Taxes other than income tax	28.6	51.4	87.9	140.2
Total Operating Expenses	370.2	375.9	1,043.8	1,058.1
INCOME FROM OPERATIONS	189.4	219.8	365.1	416.2
OTHER INCOME (EXPENSE):
Investment earnings	0.7	0.5	2.1	1.5
Other income	0.2	2.2	1.7	5.4
Other expense	(9.0)	(11.9)	(22.9)	(40.7)
Total Other Income (Expense), Net	(8.1)	(9.2)	(19.1)	(33.8)
Interest expense	33.0	34.3	100.6	105.5
INCOME BEFORE INCOME TAXES	148.3	176.3	245.4	276.9
Income tax expense	28.0	62.2	80.3	99.0
NET INCOME			165.1	177.9
NET INCOME	120.3	114.1	165.1	177.9
Derivative hedging activity
Reclassification to expenses, net of tax	0.8	1.2	2.7	3.8
Derivative hedging activity, net of tax	0.8	1.2	2.7	3.8
Total other comprehensive income	0.8	1.2	2.7	3.8
Comprehensive income (loss)	$ 121.1	$ 115.3	$ 167.8	$ 181.7

Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	$ 524.9	$ 300.2
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	411.6	277.3
Amortization of nuclear fuel	28.6	24.2
Amortization of deferred refueling outage	14.7	12.1
Amortization of deferred regulatory gain from sale leaseback	(4.1)	(4.1)
Amortization of corporate-owned life insurance	17.2	15.7
Non-cash compensation	25.2	6.7
Net deferred income taxes and credits	47.8	127.0
Allowance for equity funds used during construction	(2.4)	(1.1)
Payments for asset retirement obligations	(15.9)	(1.9)
Equity in earnings of equity method investees, net of income taxes	(4.7)	(4.9)
Other	(1.9)	(5.3)
Changes in working capital items:
Accounts receivable	(34.9)	(19.7)
Accounts receivable pledged as collateral	(15.0)	0.0
Fuel inventory and supplies	44.6	15.5
Prepaid expenses and other current assets	(3.4)	55.5
Accounts payable	(58.5)	(10.0)
Accrued taxes	119.0	35.6
Other current liabilities	38.9	(108.5)
Changes in other assets	26.0	22.9
Changes in other liabilities	33.9	5.5
Cash Flows from Operating Activities	1,191.6	742.7
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(698.3)	(564.6)
Cash acquired from the merger with Great Plains Energy	1,154.2	0.0
Purchase of securities - trusts	(107.0)	(15.3)
Sale of securities - trusts	110.2	15.9
Investment in corporate-owned life insurance	(16.2)	(16.2)
Proceeds from investment in corporate-owned life insurance	6.5	2.1
Proceeds from settlement of interest rate swap	140.6	0.0
Other investing activities	(15.2)	(3.3)
Cash Flows from (used in) Investing Activities	574.8	(581.4)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	(166.7)	(177.7)
Collateralized short-term borrowings, net	15.0	0.0
Proceeds from long-term debt	22.9	296.2
Retirements of long-term debt	(127.4)	(125.0)
Retirements of Long Term Debt Of VIEs	(28.5)	(26.8)
Repayment of capital leases	(2.9)	(2.6)
Borrowings against cash surrender value of corporate-owned life insurance	55.1	53.4
Repayment of borrowings against cash surrender value of corporate-owned life insurance	(3.9)	0.0
Distributions to shareholders of noncontrolling interests	0.0	(5.8)
Cash dividends paid	(350.4)	(166.3)
Repurchase of common stock	(486.1)	0.0
Other financing activities	(17.2)	(6.4)
Cash Flows (used in) Financing Activities	(1,090.1)	(161.0)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	676.3	0.3
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	3.5	3.2
End of period	679.8	3.5
Westar Energy Inc [Member]
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	318.5	300.2
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	281.6	277.3
Amortization of nuclear fuel	18.6	24.2
Amortization of deferred refueling outage	10.5	12.1
Amortization of deferred regulatory gain from sale leaseback	(4.1)	(4.1)
Amortization of corporate-owned life insurance	17.2	15.7
Non-cash compensation	19.9	6.7
Net deferred income taxes and credits	(34.2)	127.0
Allowance for equity funds used during construction	(2.4)	(1.1)
Payments for asset retirement obligations	(10.6)	(1.9)
Equity in earnings of equity method investees, net of income taxes	(3.7)	(4.9)
Other	(1.9)	(5.3)
Changes in working capital items:
Accounts receivable	(50.6)	(19.7)
Fuel inventory and supplies	25.4	15.5
Prepaid expenses and other current assets	(7.0)	55.5
Accounts payable	36.2	(10.0)
Accrued taxes	74.4	35.6
Other current liabilities	23.2	(108.5)
Changes in other assets	22.9	22.9
Changes in other liabilities	(26.7)	5.5
Cash Flows from Operating Activities	707.2	742.7
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(510.3)	(564.6)
Purchase of securities - trusts	(96.1)	(15.3)
Sale of securities - trusts	101.2	15.9
Investment in corporate-owned life insurance	(16.2)	(16.2)
Proceeds from investment in corporate-owned life insurance	6.5	2.1
Other investing activities	(8.1)	(3.3)
Cash Flows from (used in) Investing Activities	(523.0)	(581.4)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	48.3	(177.7)
Proceeds from long-term debt	0.0	296.2
Retirements of long-term debt	0.0	(125.0)
Retirements of Long Term Debt Of VIEs	(28.5)	(26.8)
Repayment of capital leases	(2.9)	(2.6)
Borrowings against cash surrender value of corporate-owned life insurance	55.1	53.4
Repayment of borrowings against cash surrender value of corporate-owned life insurance	(3.9)	0.0
Distributions to shareholders of noncontrolling interests	0.0	(5.8)
Cash dividends paid	(235.1)	(166.3)
Other financing activities	(17.3)	(6.4)
Cash Flows (used in) Financing Activities	(184.3)	(161.0)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(0.1)	0.3
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	3.5	3.2
End of period	3.4	3.5
KCPL [Member]
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:
Net income	165.1	177.9
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	209.0	199.9
Amortization of nuclear fuel	18.7	24.1
Amortization of deferred refueling outage	10.3	13.7
Net deferred income taxes and credits	25.2	32.6
Allowance for equity funds used during construction	(1.2)	(3.4)
Payments for asset retirement obligations	(9.9)	(14.9)
Other	2.7	6.3
Changes in working capital items:
Accounts receivable	(41.0)	(19.5)
Accounts receivable pledged as collateral	0.0	(20.0)
Fuel inventory and supplies	13.2	3.6
Prepaid expenses and other current assets	(3.6)	8.9
Accounts payable	(97.7)	(75.1)
Accrued taxes	97.9	122.7
Other current liabilities	8.5	9.9
Changes in other assets	28.3	52.6
Changes in other liabilities	79.0	7.3
Cash Flows from Operating Activities	504.5	526.6
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	(310.6)	(317.1)
Purchase of securities - trusts	(27.9)	(23.8)
Sale of securities - trusts	22.5	21.3
Other investing activities	3.4	0.8
Cash Flows from (used in) Investing Activities	(312.6)	(318.8)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Short term debt, net	40.3	(60.9)
Collateralized short-term borrowings, net	0.0	20.0
Proceeds from long-term debt	319.5	296.2
Retirements of long-term debt	(373.4)	(281.0)
Cash dividends paid	(180.0)	(182.0)
Other financing activities	2.9	0.0
Cash Flows (used in) Financing Activities	(190.7)	(207.7)
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	1.2	0.1
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of period	2.2	4.5
End of period	$ 3.4	$ 4.6

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Restricted cash	$ 0.1	$ 0.1	$ 0.1	$ 0.1
Westar Energy Inc [Member]
Restricted cash	$ 0.1	$ 0.1	$ 0.1	$ 0.1

Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	Westar Energy Inc [Member]	Westar Energy Inc [Member] Common Stock [Member]	Westar Energy Inc [Member] Retained Earnings [Member]	Westar Energy Inc [Member] Noncontrolling Interest [Member]	KCPL [Member]	KCPL [Member] Common Stock [Member]	KCPL [Member] Retained Earnings [Member]	KCPL [Member] AOCI - Net gains (losses) on cash flow hedges [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption of ASU 2016-09									$ (0.7)		$ (0.7)
Beginning balance (in shares) at Dec. 31, 2016		141,791,153				141,791,153				1
Beginning balance at Dec. 31, 2016	$ 3,833.2	$ 2,727.3	$ 1,078.6	$ 27.3	$ 3,833.2	$ 2,727.3	$ 1,078.6	$ 27.3	2,541.5	$ 1,563.1	982.6	$ (4.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	300.2		290.0	10.2	300.2		290.0	10.2	177.9		177.9
Issuance of stock	0.6	$ 0.6			0.6	$ 0.6
Issuance of stock (in shares)		12,131				12,131
Issuance of stock for compensation and reinvested dividends (in shares)		290,892				290,892
Issuance of stock for compensation and reinvested dividends	4.9	$ 4.9			4.9	$ 4.9
Tax withholding related to stock compensation	(7.0)	(7.0)			(7.0)	(7.0)
Dividends declared on common stock	(172.1)		(172.1)		(172.1)		(172.1)		(182.0)		(182.0)
Stock compensation expense	6.7	$ 6.7			6.7	$ 6.7
Deconsolidation of noncontrolling interests	(81.9)			(81.9)	(81.9)			(81.9)
Distributions to shareholders of noncontrolling interests	(5.7)			(5.7)	(5.7)			(5.7)
Derivative hedging activity, net of tax									3.8			3.8
Ending balance (in shares) at Sep. 30, 2017		142,094,176				142,094,176				1
Ending balance at Sep. 30, 2017	3,878.9	$ 2,732.5	1,196.5	(50.1)	3,878.9	$ 2,732.5	1,196.5	(50.1)	2,540.5	$ 1,563.1	977.8	(0.4)
Beginning balance (in shares) at Dec. 31, 2017		142,094,275				142,094,275				1
Beginning balance at Dec. 31, 2017	3,860.4	$ 2,734.8	1,173.3	(47.7)	3,860.4	$ 2,734.8	1,173.3	(47.7)	2,513.2	$ 1,563.1	949.7	0.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	524.9		517.3	7.6	318.5		310.9	7.6	165.1		165.1
Issuance of stock to Great Plains Energy shareholders (in shares)		128,947,518
Issuance of stock to Great Plains Energy shareholders	6,979.9	$ 6,979.9
Issuance of restricted common stock (in shares)		122,505
Issuance of stock for compensation and reinvested dividends (in shares)		528,359				516,990
Issuance of stock for compensation and reinvested dividends	0.4	$ 0.4			0.0
Tax withholding related to stock compensation	(17.2)	(17.2)			(17.2)	$ (17.2)
Dividends declared on common stock	(237.5)		(237.5)		(181.5)		(181.5)		(180.0)		(180.0)
Dividend equivalents declared	(0.6)		(0.6)
Stock compensation expense	25.2	25.2			19.9	$ 19.9
Repurchase of common stock	(486.1)	$ (486.1)
Repurchase of common stock		(6,895,073)
Stock cancelled pursuant to Amended Merger Agreement (in shares)						(142,611,264)
Stock cancelled pursuant to Amended Merger Agreement					0.0
Derivative hedging activity, net of tax									2.7			2.7
Other	(0.6)	$ (0.6)			0.1	$ 0.1
Ending balance (in shares) at Sep. 30, 2018		264,797,584				1				1
Ending balance at Sep. 30, 2018	$ 10,648.8	$ 9,236.4	$ 1,452.5	$ (40.1)	$ 4,000.2	$ 2,737.6	$ 1,302.7	$ (40.1)	$ 2,501.0	$ 1,563.1	$ 934.8	$ 3.1

Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Dividends declared on common stock (in dollars per share)	$ 1.26	$ 1.20
Westar Energy Inc [Member]
Dividends declared on common stock (in dollars per share)		$ 1.20

Organization and Basis of Presentation

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Organization and Basis of Presentation

1. ORGANIZATION AND BASIS OF PRESENTATION

Organization

Evergy is a public utility holding company incorporated in 2017 and headquartered in Kansas City, Missouri. Evergy operates primarily through the following wholly-owned direct subsidiaries:


•	Westar Energy is an integrated, regulated electric utility that provides electricity to customers in the state of Kansas. Westar Energy has one active wholly-owned subsidiary with significant operations, Kansas Gas and Electric Company (KGE).


•	KCP&L is an integrated, regulated electric utility that provides electricity to customers in the states of Missouri and Kansas. KCP&L has one active wholly-owned subsidiary, Kansas City Power & Light Receivables Company (KCP&L Receivables Company).


•	KCP&L Greater Missouri Operations Company (GMO) is an integrated, regulated electric utility that provides electricity to customers in the state of Missouri. GMO also provides regulated steam service to certain customers in the St. Joseph, Missouri area. GMO has one active wholly-owned subsidiary, GMO Receivables Company.


•	GPE Transmission Holding Company, LLC (GPETHC) owns 13.5% of Transource Energy, LLC (Transource) with the remaining 86.5% owned by AEP Transmission Holding Company, LLC, a subsidiary of American Electric Power Company, Inc. (AEP). Transource is focused on the development of competitive electric transmission projects. GPETHC accounts for its investment in Transource under the equity method.

Westar Energy also owns a 50% interest in Prairie Wind Transmission, LLC (Prairie Wind), which is a joint venture between Westar Energy and affiliates of AEP and Berkshire Hathaway Energy Company. Prairie Wind owns a 108-mile, 345 kV double-circuit transmission line that is now being used to provide transmission service in the Southwest Power Pool, Inc. (SPP). Westar Energy accounts for its investment in Prairie Wind under the equity method.

Westar Energy and KGE conduct business in their respective service territories using the name Westar Energy. KCP&L and GMO conduct business in their respective service territories using the name KCP&L. Collectively, the Evergy Companies have approximately 12,300 MWs of owned generating capacity and engage in the generation, transmission, distribution and sale of electricity to approximately 1.6 million customers in the states of Kansas and Missouri.

Evergy was incorporated in 2017 as Monarch Energy Holding, Inc. (Monarch Energy), a wholly-owned subsidiary of Great Plains Energy Incorporated (Great Plains Energy). Prior to the closing of the merger transactions, Monarch Energy changed its name to Evergy and did not conduct any business activities other than those required for its formation and matters contemplated by the Amended and Restated Agreement and Plan of Merger, dated as of July 9, 2017, by and among Great Plains Energy, Westar Energy, Monarch Energy and King Energy, Inc. (King Energy), a wholly-owned subsidiary of Monarch Energy (Amended Merger Agreement). On June 4, 2018, in accordance with the Amended Merger Agreement, Great Plains Energy merged into Evergy, with Evergy surviving the merger and King Energy merged into Westar Energy, with Westar Energy surviving the merger. These merger transactions resulted in Evergy becoming the parent entity of Westar Energy and the direct subsidiaries of Great Plains Energy, including KCP&L and GMO. See Note 2 for additional information regarding the merger.

Principles of Consolidation

Westar Energy was determined to be the accounting acquirer in the merger and thus, the predecessor of Evergy. Therefore, Evergy's consolidated financial statements reflect the results of operations of Westar Energy for the three months ended and year to date September 30, 2017 and the financial position of Westar Energy as of December 31, 2017. Evergy had separate operations for the period beginning with the quarter ended June 30, 2018, and references to amounts for periods after the closing of the merger relate to Evergy. The results of Great Plains Energy's direct subsidiaries have been included in Evergy's results of operations from the date of the closing of the merger and thereafter.

KCP&L and Westar Energy will continue to maintain their current reporting requirements as Securities and Exchange Commission (SEC) registrants. KCP&L has elected not to apply "push-down accounting" related to the merger, whereby the adjustments of assets and liabilities to fair value and the resulting goodwill would be recorded on the financial statements of the acquired subsidiary. These adjustments for KCP&L, as well as those related to the acquired assets and liabilities of Great Plains Energy and its other direct subsidiaries, are reflected at consolidated Evergy.

Each of Evergy's, Westar Energy's and KCP&L's consolidated financial statements includes the accounts of their subsidiaries and variable interest entities (VIEs) of which they are the primary beneficiary. Undivided interests in jointly-owned generation facilities are included on a proportionate basis. Intercompany transactions have been eliminated. The Evergy Companies assess financial performance and allocate resources on a consolidated basis (i.e., operate in one segment).

In preparing financial statements that conform to generally accepted accounting principles (GAAP), management must make estimates and assumptions that affect the reported amounts of assets and liabilities, the reported amounts of revenues and expenses, and the disclosure of contingent assets and liabilities at the date of the financial statements. Actual results could differ from those estimates.

These unaudited consolidated financial statements have been prepared in accordance with GAAP for the United States of America for interim financial information and with the instructions to Form 10-Q and Regulation S-X. Accordingly, these unaudited consolidated financial statements do not include all of the information and notes required by GAAP for annual financial statements. Because the unaudited consolidated financial statements and notes do not include all of the information and notes required by GAAP for annual financial statements, the unaudited consolidated financial statements and other information included in this quarterly report should be read in conjunction with the Westar Energy First Quarter 2018 Quarterly Report on Form 10-Q, the Great Plains Energy and KCP&L combined First Quarter 2018 Quarterly Report on Form 10-Q, the Westar Energy 2017 Form 10-K and the Great Plains Energy and KCP&L combined 2017 Form 10-K.

Certain changes in classification and corresponding reclassification of prior period data were made in Evergy's, Westar Energy's and KCP&L's unaudited consolidated balance sheets, statements of income and comprehensive income and unaudited statements of cash flows for comparative purposes. Evergy reflects the classifications of Westar Energy as the accounting acquirer in the merger. These reclassifications did not affect Evergy's, Westar Energy's or KCP&L's net income or Evergy's, Westar Energy's or KCP&L's cash flows from operations, investing or financing.

Most significantly for Westar Energy's consolidated balance sheets as of December 31, 2017 was the reclassification of $50.2 million from accrued employee benefits (currently reported as pension and post-retirement liability) to other long-term liabilities. Most significantly for KCP&L's consolidated balance sheets, current regulatory assets and liabilities have been presented separately from the non-current portions in each respective consolidated balance sheet where recovery or refund is expected within the next 12 months.

The table below summarizes KCP&L's reclassifications related to operating and investing activities for its consolidated statement of cash flows for year to date September 30, 2017.



	Year to Date
	September 30, 2017
	As Filed			Updated
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:	(in millions)
Adjustments to reconcile income to net cash from operating activities:
Amortization of other	$	23.4		$	—
Amortization of deferred refueling outage	—			13.7
Deferred income taxes, net	33.4			—
Investment tax credit amortization	(0.8		)	—
Net deferred income taxes and credits	—			32.6
Payments for asset retirement obligations	—			(14.9		)
Other^(a)	(16.0		)	6.3
Changes in working capital items:
Fuel inventory and supplies	—			3.6
Fuel inventories^(a)	10.8			—
Materials and supplies^(a)	(7.2		)	—
Prepaid expenses and other current assets	—			8.9
Accrued interest^(a)	8.1			—
Other current liabilities	—			9.9
Changes in other assets	—			52.6
Changes in other liabilities	—			7.3
Deferred refueling outage costs^(a)	12.1			—
Pension and post-retirement benefit obligations^(a)	48.6			—
Fuel recovery mechanisms^(a)	7.6			—
Total reclassifications	$	120.0		$	120.0
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	$	—		$	(317.1	)
Utility capital expenditures	(295.1		)	—
Allowance for borrowed funds used during construction	(4.2		)	—
Other investing activities	(17.0		)	0.8
Total reclassifications	$	(316.3	)	$	(316.3	)

^(a)Previously reported within Note 3 to the consolidated financial statements of the Great Plains Energy and KCP&L combined Third Quarter 2017 Quarterly Report on Form 10-Q.

Fuel Inventory and Supplies

The Evergy Companies record fuel inventory and supplies at average cost. The balances for fuel inventory and supplies are stated separately in the table below.



	September 30			December 31
		2018			2017
Evergy		(millions)
Fuel inventory		$	163.1		$	94.1
Supplies		357.8			199.5
Fuel inventory and supplies		$	520.9		$	293.6
Westar Energy
Fuel inventory		$	84.9		$	94.1
Supplies		183.8			199.5
Fuel inventory and supplies		$	268.7		$	293.6
KCP&L^(a)
Fuel inventory		$	54.6		$	71.0
Supplies		129.2			126.0
Fuel inventory and supplies		$	183.8		$	197.0

^(a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Property, Plant and Equipment

The following tables summarize the property, plant and equipment of Evergy, Westar Energy and KCP&L.



September 30, 2018	Evergy			Westar Energy			KCP&L
	(millions)
Electric plant in service	$	27,290.0		$	13,236.1		$	10,594.2
Electric plant acquisition adjustment	740.6			740.6			—
Accumulated depreciation	(10,168.2		)	(4,838.9		)	(4,172.3		)
Plant in service	17,862.4			9,137.8			6,421.9
Construction work in progress	723.5			443.6			183.4
Nuclear fuel, net	109.1			54.1			55.0
Plant to be retired, net^(b)	141.0			2.0			—
Property, plant and equipment, net	$	18,836.0		$	9,637.5		$	6,660.3

December 31, 2017	Evergy			Westar Energy			KCP&L^(a)
	(millions)
Electric plant in service	$	12,954.3		$	12,954.3		$	10,213.2
Electric plant acquisition adjustment	739.0			739.0			—
Accumulated depreciation	(4,651.7		)	(4,651.7		)	(4,070.3		)
Plant in service	9,041.6			9,041.6			6,142.9
Construction work in progress	434.9			434.9			350.3
Nuclear fuel, net	71.4			71.4			72.4
Plant to be retired, net^(b)	5.9			5.9			—
Property, plant and equipment, net	$	9,553.8		$	9,553.8		$	6,565.6

^(a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

^(b) As of September 30, 2018, represents the planned retirement of GMO's Sibley No. 3 Unit and Westar Energy analog meters prior to the end of their remaining useful lives. As of December 31, 2017, represents the planned retirement of Westar Energy analog meters prior to the end of their remaining useful lives.

Earnings Per Share

Evergy has participating securities in the form of unvested restricted share units (RSUs) with nonforfeitable rights to dividend equivalents that receive dividends on an equal basis with dividends declared on common stock. As a result, Evergy applies the two-class method of computing basic and diluted earnings per share (EPS).

To compute basic EPS, Evergy divides the earnings allocated to common stock by the weighted average number of common shares outstanding. Diluted EPS includes the effect of issuable common shares resulting from RSUs with forfeitable rights to dividend equivalents, performance shares and restricted stock. Evergy computes the dilutive effects of potential issuances of common shares using the treasury stock method.

The following table reconciles Evergy's basic and diluted EPS.



	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Income	(millions, except per share amounts)
Net income	$	357.6	$	160.7	$	524.9	$	300.2
Less: net income attributable to noncontrolling interests	2.6		2.4		7.6		10.2
Net income attributable to Evergy, Inc.	355.0		158.3		517.3		290.0
Less: net income allocated to RSUs	0.2		0.3		0.4		0.5
Net income allocated to common stock	$	354.8	$	158.0	$	516.9	$	289.5
Common Shares Outstanding
Weighted average equivalent common shares outstanding - basic	268.6		142.5		197.9		142.5
Add: effect of dilutive securities	0.2		—		0.1		—
Weighted average equivalent common shares outstanding - diluted	268.8		142.5		198.0		142.5
Basic and Diluted EPS	$	1.32	$	1.11	$	2.61	$	2.03

There were no anti-dilutive securities excluded from the computation of diluted EPS for the three months ended and year to date September 30, 2018 and 2017.

Dividends Declared

In November 2018, Evergy's Board of Directors (Evergy Board) declared a quarterly dividend of $0.475 per share on Evergy's common stock. The common dividend is payable December 20, 2018, to shareholders of record as of November 29, 2018.

In November 2018, Westar Energy's Board of Directors declared a cash dividend payable to Evergy of $70.0 million, payable on December 19, 2018.

Supplemental Cash Flow Information



Year to Date September 30	2018			2017
Evergy	(millions)
Cash paid for (received from):
Interest, net of amounts capitalized	$	148.7		$	109.0
Interest of VIEs	2.3			3.1
Income taxes, net of refunds	0.6			(12.6		)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(24.8		)	112.5
Deconsolidation of property, plant and equipment of VIE	—			(72.9		)
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	0.4			4.9
Deconsolidation of VIE	—			(83.1		)
Assets acquired through capital leases	0.1			4.6
Westar Energy
Cash paid for (received from):
Interest, net of amounts capitalized	$	110.5		$	109.0
Interest of VIEs	2.3			3.1
Income taxes, net of refunds	—			(12.6		)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(42.0		)	112.5
Deconsolidation of property, plant and equipment of VIE	—			(72.9		)
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	—			4.9
Deconsolidation of VIE	—			(83.1		)
Assets acquired through capital leases	0.1			4.6
KCP&L^(a)
Cash paid for (received from):
Interest, net of amounts capitalized	$	87.6		$	88.6
Income taxes, net of refunds	28.4			4.9
Non-cash investing transactions:
Property, plant and equipment additions	15.2			15.5

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

See Note 2 for the non-cash information related to the merger transaction, including the fair value of Great Plains Energy's assets acquired and liabilities assumed and the issuance of Evergy common stock.

New Accounting Standards

Intangibles - Internal-Use Software

In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which aligns the requirements for recording implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. An entity in a hosting arrangement that is a service contract will need to determine which project stage (that is, preliminary project stage, application development stage or post-implementation stage) an implementation activity relates. Costs for implementation activities in the application development stage are recorded as a prepaid asset depending on the nature of the costs, while costs incurred during the preliminary project and post-implementation stages are expensed as the activities are incurred. Costs that are recorded to a prepaid asset are to be expensed over the term of the hosting arrangement. The new guidance is effective for annual periods beginning after December 15, 2019 and interim periods within those fiscal years. The new guidance can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. Early adoption is permitted. The Evergy Companies are currently evaluating the new guidance including the timing of adoption.

Compensation - Retirement Benefits

In March 2017, the FASB issued ASU No. 2017-07, Compensation-Retirement Benefits, which requires an employer to disaggregate the service cost component from the other components of net benefit cost. The service cost component is to be reported in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The non-service cost components are to be reported separately from service costs and outside of a subtotal of income from operations. The amendments in this update allow only the service cost component to be eligible for capitalization as part of utility plant. The non-service cost components that are no longer eligible for capitalization as part of utility plant will be recorded as a regulatory asset. The new guidance is to be applied retrospectively for the presentation of service cost and non-service cost components in the income statement and prospectively for the capitalization of the service cost component and is effective for interim and annual periods beginning after December 15, 2017. The Evergy Companies adopted ASU No. 2017-07 on January 1, 2018, and accordingly have retrospectively adjusted prior periods. The Evergy Companies utilized the practical expedient that allows for the use of amounts disclosed in Note 7 for applying the retrospective presentation to the 2017 consolidated statements of income and comprehensive income.

The following table reflects the retrospective adjustments in the line items of the Evergy Companies' consolidated statements of income and comprehensive income associated with the adoption of ASU No. 2017-07.



	Three Months Ended									Year to Date
	September 30, 2017									September 30, 2017
	As Previously Reported^(b)			Effect of Change			As Reported			As Previously Reported^(b)			Effect of Change			As Reported
Evergy	(millions)
Operating and maintenance expense	$	145.5		$	(4.9	)	$	140.6		$	430.6		$	(15.0	)	$	415.6
Total operating expenses	534.3			(4.9		)	529.4			1,434.7			(15.0		)	1,419.7
Income from operations	260.0			4.9			264.9			541.5			15.0			556.5
Other expense	(6.6		)	(4.9		)	(11.5		)	(14.6		)	(15.0		)	(29.6		)
Total other income (expense), net	(1.7		)	(4.9		)	(6.6		)	(5.4		)	(15.0		)	(20.4		)
Westar Energy
Operating and maintenance expense	$	145.5		$	(4.9	)	$	140.6		$	430.6		$	(15.0	)	$	415.6
Total operating expenses	534.3			(4.9		)	529.4			1,434.7			(15.0		)	1,419.7
Income from operations	260.0			4.9			264.9			541.5			15.0			556.5
Other expense	(6.6		)	(4.9		)	(11.5		)	(14.6		)	(15.0		)	(29.6		)
Total other income (expense), net	(1.7		)	(4.9		)	(6.6		)	(5.4		)	(15.0		)	(20.4		)
KCP&L^(a)
Operating and maintenance expense	$	124.2		$	(9.9	)	$	114.3		$	385.0		$	(34.3	)	$	350.7
Total operating expenses	385.8			(9.9		)	375.9			1,092.4			(34.3		)	1,058.1
Income from operations	209.9			9.9			219.8			381.9			34.3			416.2
Other expense	(2.0		)	(9.9		)	(11.9		)	(6.4		)	(34.3		)	(40.7		)
Total other income (expense), net	0.7			(9.9		)	(9.2		)	0.5			(34.3		)	(33.8		)

^(a)KCP&L amounts are not included in consolidated Evergy for the three months ended and year to date September 30, 2017.

^(b)Certain Evergy, Westar Energy, and KCP&L as previously reported amounts have been adjusted to reflect reclassification adjustments made for comparative purposes as discussed further in Principles of Consolidation above and that have no impact on net income.

Statement of Cash Flows

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments, which clarifies how certain cash receipts and cash payments are presented and classified in the statement of cash flows. Among other clarifications, the guidance requires that cash proceeds received from the settlement of corporate-owned life insurance (COLI) policies be classified as cash inflows from investing activities and that cash payments for premiums on COLI policies may be classified as cash outflows for investing activities, operating activities or a combination of both. Retrospective application is required. The Evergy Companies adopted the guidance effective January 1, 2018, which resulted in retrospective reclassification of cash proceeds of $1.9 million from the settlement of COLI policies from cash inflows from operating activities to cash inflows from investing activities for year to date September 30, 2017, for Evergy and Westar Energy. In addition, cash payments of $2.3 million for premiums on COLI policies were reclassified from cash outflows used in operating activities to cash outflows used in investing activities for the same period for Evergy and Westar Energy. The adoption of ASU No. 2016-15 did not have a material impact on KCP&L.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows: Restricted Cash, which requires that the statement of cash flows explains the change for the period of restricted cash and restricted cash equivalents along with cash and cash equivalents. The guidance requires a retrospective transition method and is effective for fiscal years beginning after December 15, 2017. The Evergy Companies adopted the guidance effective January 1, 2018. As a result, Evergy and Westar Energy adjusted amounts previously reported for cash and cash equivalents to include restricted cash which resulted in an increase to beginning and ending cash, cash equivalents and restricted cash of $0.1 million for year to date September 30, 2017. The adoption of ASU No. 2016-18 did not have a material impact on KCP&L.

Leases

In February 2016, the FASB issued ASU No. 2016-02, Leases, which requires an entity that is a lessee to record a right-of-use asset and a lease liability for lease payments on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The new guidance is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted, and requires a modified retrospective transition approach with an option to either adjust or not adjust comparative periods. The Evergy Companies plan to adopt the new guidance on January 1, 2019, without adjusting comparative periods. In 2016, management began evaluating current leases to assess the initial impact on Evergy's consolidated financial results. The Evergy Companies continue to evaluate the guidance and disclosure requirements and believe application of the guidance will result in an increase to the assets and liabilities on their consolidated balance sheets, with minimal impact to their consolidated statements of income and comprehensive income. In addition, management is evaluating the Evergy Companies' internal controls over financial reporting as needed to ensure that they remain effective after implementation. The standard permits an entity to elect a practical expedient for existing or expired contracts to forgo reassessing leases to determine whether each is in scope of the new standard and to forgo reassessing lease classification. The Evergy Companies expect to elect this practical expedient upon implementation. In July 2018, the FASB issued ASU No. 2018-11, which provides entities an optional transition method to apply ASU No. 2016-02 as of the date of initial application of the standard rather than as of the earliest period presented. The Evergy Companies are evaluating this update and have not yet determined if they will elect to use this optional transition method.

Financial Instruments

In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall: Recognition and Measurement of Financial Assets and Financial Liabilities, which generally requires equity investments to be measured at fair value with changes in fair value recognized in net income. Under the new standard, equity securities are no longer to be classified as available-for-sale or trading securities. The guidance requires a modified retrospective transition method. This guidance is effective for fiscal years beginning after December 15, 2017; accordingly, the Evergy Companies adopted the new standard on January 1, 2018, without a material impact on their consolidated financial statements.

Revenue Recognition

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. In August 2015, the FASB issued ASU No. 2015-14, deferring the effective date of ASU No. 2014-09 one year, from January 1, 2017, to January 1, 2018. The ASU replaced most existing revenue recognition guidance in GAAP when it became effective. The Evergy Companies adopted ASU No. 2014-09 and its related amendments (ASC 606) on January 1, 2018, using the modified retrospective transition method for all contracts not completed as of the date of adoption. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606 while historical periods have not been adjusted and continue to be reported in accordance with the legacy guidance in ASC 605 - Revenue Recognition.

There was no cumulative effect adjustment to the opening balance of retained earnings in 2018 for the Evergy Companies as a result of the adoption of the new guidance. The impact to both operating revenues and taxes other than income taxes on KCP&L's statements of comprehensive income in 2018 as a result of adopting ASC 606 was a decrease of $22.1 million and $59.7 million for the three months ended and year to date September 30, 2018, respectively. This impact was related to sales taxes and franchise fees collected from KCP&L's Missouri customers, which prior to ASC 606, were recorded gross on KCP&L's statements of comprehensive income. See Note 3 for more information on revenue from contracts with customers.

Merger of Great Plains Energy and Westar Energy

9 Months Ended

Sep. 30, 2018

Business Combinations [Abstract]

Merger of Great Plains Energy and Westar Energy

2. MERGER OF GREAT PLAINS ENERGY AND WESTAR ENERGY

Description of Merger Transaction

On June 4, 2018, Evergy completed the mergers contemplated by the Amended Merger Agreement. As a result of the mergers, Great Plains Energy merged into Evergy, with Evergy surviving the merger and King Energy merged into Westar Energy, with Westar Energy surviving the merger. Following the completion of these mergers, Westar Energy and the direct subsidiaries of Great Plains Energy, including KCP&L and GMO, became wholly-owned subsidiaries of Evergy.

The merger was structured as a merger of equals in a tax-free exchange of shares that involved no premium paid or received with respect to either Great Plains Energy or Westar Energy. As a result of the closing of the merger transaction, each outstanding share of Great Plains Energy common stock was converted into 0.5981 shares of Evergy common stock and each outstanding share of Westar Energy common stock was converted into 1 share of Evergy common stock.

As provided in the Amended Merger Agreement, substantially all of Westar Energy's outstanding equity compensation awards vested and were converted into a right to receive Evergy common stock and all of Great Plains Energy's outstanding equity compensation awards were converted into equivalent Evergy awards subject to the same terms and conditions at the Great Plains Energy merger exchange ratio of 0.5981.

Merger Related Regulatory Matters

KCC

In May 2018, the State Corporation Commission of the State of Kansas (KCC) approved Great Plains Energy's, KCP&L's and Westar Energy's joint application for approval of the merger, including a settlement agreement that had been reached between Great Plains Energy, KCP&L, Westar Energy, KCC staff and certain other intervenors in the case. Through the joint application and settlement agreement, Great Plains Energy, KCP&L and Westar Energy agreed to the conditions and obligations listed below, in addition to other organizational, financing, customer service and civic responsibility commitments.


•	Provide a total of $30.6 million of one-time bill credits to Kansas electric retail customers as soon as practicable following the close of the merger and the completion of Westar Energy's and KCP&L's current rate cases in Kansas. Of this total, $23.1 million of the credits relate to Westar Energy customers and the remaining $7.5 million of credits relate to KCP&L Kansas customers.


•	Provide a total of approximately $46 million in additional bill credits consisting of $11.5 million in annual bill credits to Kansas electric retail customers from 2019 through 2022. Of the annual amount, $8.7 million of the credits relate to Westar Energy customers and the remaining $2.8 million of credits relate to KCP&L Kansas customers.


•	Provide for the inclusion of a total of $30.0 million of merger-related savings in Westar Energy's and KCP&L's current rate cases in Kansas. Of this total, $22.5 million of the savings are attributable to Westar Energy with the remaining $7.5 million of savings attributable to KCP&L's Kansas jurisdiction.


•	A five year base rate moratorium for Westar Energy and KCP&L in Kansas that will commence following the conclusion of KCP&L's current Kansas rate case, expected in December 2018. The moratorium is subject to certain conditions and does not include Westar Energy's or KCP&L's fuel recovery mechanisms and certain other cost recovery mechanisms in Kansas.


•	Require both Westar Energy and KCP&L to file rate cases in Kansas in a fashion that would allow for updated electric utility rates to become effective upon the end of the five-year rate moratorium in December 2023.


•	Participate in an Earnings Review and Sharing Plan (ERSP) for the years 2019 through 2022, which may result in Westar Energy and/or KCP&L being subject to refunding 50% of earned return on equity in excess of authorized return on equity to their Kansas customers.


•	Maintain charitable contributions and community involvement in the Kansas service territories of Westar Energy and KCP&L at levels equal to or greater than their respective 2015 levels for 5 years following the closing of the merger.


•	Commit that Westar Energy's and KCP&L's retail electric base rates will not increase as a result of the merger.


•	Allow Westar Energy and KCP&L to recover a total of $30.9 million of merger transition costs consisting of $23.2 million for Westar Energy and $7.7 million for KCP&L's Kansas jurisdiction. Westar Energy and KCP&L have recorded these amounts as regulatory assets and the settlement agreement stipulates that they will be recovered over a ten year period.

MPSC

In May 2018, the Public Service Commission of the State of Missouri (MPSC) approved Great Plains Energy's, KCP&L's, GMO's and Westar Energy's joint application for approval of the merger, including two stipulations and agreements between these companies, MPSC staff and certain other intervenors in the case. Through the joint application and stipulations and agreements, Great Plains Energy, KCP&L, GMO and Westar Energy agreed to the conditions and obligations listed below, in addition to other organizational, financing, customer service and civic responsibility commitments.


•	Provide a total of $29.1 million of one-time bill credits to Missouri electric retail customers within 120 days following the close of the merger. Of this total, $14.9 million of the credits relate to KCP&L Missouri customers and the remaining $14.2 million of credits relate to GMO customers.


•	Commit that KCP&L's and GMO's retail electric base rates will not increase as a result of the merger.


•	Maintain charitable contributions and community involvement in the Missouri service territories of KCP&L and GMO at levels equal to or greater than their respective 2015 levels for 5 years following the closing of the merger.


•	Provide a total of $3.0 million of support over 10 years to community agencies to promote low-income weatherization efforts.


•	Support the recovery of a total of $16.9 million of merger transition costs in KCP&L's and GMO's current rate cases, consisting of $9.7 million for KCP&L's Missouri jurisdiction and $7.2 million for GMO. KCP&L and GMO have recorded these amounts as regulatory assets and it is expected that they will be recovered over a ten year period.

Accounting Charges and Deferrals Related to the Merger

The following pre-tax reductions of revenue, expenses and deferral were recognized following the consummation of the merger and are included in the Evergy Companies' consolidated statements of income and comprehensive income for year to date September 30, 2018.



Description	Income Statement Line Item	Expected Payment Period	Evergy			Westar Energy			KCP&L
			(millions)
One-time bill credits	Operating revenues	2018 - 2019	$	(59.7	)	$	(23.1	)	$	(22.4	)
Annual bill credits	Operating revenues	2019 - 2022	(7.6		)	(5.8		)	(1.9		)
Total impact to operating revenues			$	(67.3	)	$	(28.9	)	$	(24.3	)

Charitable contributions and community support	Operating and maintenance	2018 - 2027	$	24.7		$	—		$	—
Voluntary severance and accelerated equity compensation	Operating and maintenance	2018 - 2019	40.7			40.7			—
Other transaction and transition costs	Operating and maintenance	2018	47.0			20.4			1.7
Reallocation and deferral of merger transition costs	Operating and maintenance	n/a	(47.8		)	(13.3		)	(23.9		)
Total impact to operating and maintenance expense			$	64.6		$	47.8		$	(22.2	)
Total			$	(131.9	)	$	(76.7	)	$	(2.1	)

Reductions of revenue and expenses related to customer bill credits, charitable contributions and community support were incurred as a result of conditions in the MPSC and KCC merger orders and were recorded as liabilities in the amounts presented above following the consummation of the merger. Voluntary severance and accelerated equity compensation represent costs related to payments for voluntary severance and change in control plans, as well as the recording of unrecognized equity compensation costs and the incremental fair value associated with the vesting of outstanding Westar Energy equity compensation awards. Other transaction and transition costs include merger success fees and fees for other outside services incurred. Reallocation and deferral of merger transition costs represents the net reallocation of incurred merger transition costs between Evergy, Westar Energy, KCP&L and GMO and the subsequent deferral of these transition costs to a regulatory asset for future recovery in accordance with the KCC and MPSC merger orders.

Purchase Price

Based on an evaluation of the provisions of ASC 805, Business Combinations, Westar Energy was determined to be the accounting acquirer in the merger. Pursuant to the Amended Merger Agreement, Great Plains Energy's common stock shares were exchanged for Evergy common stock shares at the fixed exchange rate of 0.5981. The total consideration transferred in the merger is based on the closing stock price of Westar Energy on June 4, 2018 and is calculated as follows.



	(millions, except share amounts)
Great Plains Energy common stock shares outstanding as of June 4, 2018	215,800,074
Great Plains Energy restricted stock awards outstanding as of June 4, 2018	(204,825		)
Great Plains Energy shares to be converted to Evergy shares	215,595,249
Exchange ratio	0.5981
Evergy common stock shares issued to Great Plains Energy shareholders	128,947,518
Closing price of Westar Energy common stock as of June 4, 2018	$	54.00
Fair value of Evergy shares issued to Great Plains Energy shareholders	$	6,963.2
Fair value of Great Plains Energy's equity compensation awards	12.5
Total purchase price	$	6,975.7

Great Plains Energy's equity compensation awards, including performance shares and restricted stock, were replaced by equivalent Evergy equity compensation awards subject to substantially the same terms and conditions upon the closing of the merger. In accordance with the accounting guidance in ASC 805, a portion of the fair value of these awards is attributable to the purchase price as it represents consideration transferred in the merger.

Purchase Price Allocation

The fair value of Great Plains Energy's assets acquired and liabilities assumed as of June 4, 2018 was determined based on significant estimates and assumptions that are judgmental in nature. Third-party valuation specialists were engaged to assist in the valuation of these assets and liabilities. The fair values of Great Plains Energy's assets acquired and liabilities assumed utilized for the purchase price allocation are preliminary to the extent that additional information is obtained about facts and circumstances that existed as of the acquisition date.

The significant assets and liabilities for which preliminary valuation amounts are reflected as of the filing of this combined Form 10-Q include the fair value of acquired long-term debt, asset retirement obligations, pension and post-retirement plans, accumulated deferred income tax liabilities and certain other long-term assets and liabilities.

The majority of Great Plains Energy's operations are subject to the rate-setting authority of the MPSC, KCC and The Federal Energy Regulatory Commission (FERC) and are accounted for pursuant to GAAP, including the accounting guidance for regulated operations. The rate-setting and cost recovery provisions for Great Plains Energy's regulated operations provide revenue derived from costs including a return on investment of assets and liabilities included in rate base. Except for the significant assets and liabilities for which valuation adjustments were made as discussed above, the fair values of Great Plains Energy's tangible and intangible assets and liabilities subject to these rate-setting provisions approximate their carrying values and the assets and liabilities do not reflect any adjustments to these amounts other than for amounts not included in rate base. The difference between the fair value and pre-merger carrying amounts for Great Plains Energy's long-term debt, asset retirement obligations and pension and post-retirement plans that were related to regulated operations were recorded as a regulatory asset or liability. The excess of the purchase price over the estimated fair values of the assets acquired and liabilities assumed was recognized as goodwill as of the merger date.

The preliminary purchase price allocation to Great Plains Energy's assets and liabilities as of June 4, 2018 is detailed in the following table.



	(millions)
Current assets	$	2,151.7
Property, plant and equipment, net	9,179.7
Goodwill	2,333.5
Other long-term assets, excluding goodwill	1,235.9
Total assets	$	14,900.8
Current liabilities	1,673.9
Long-term liabilities, excluding long-term debt	2,892.6
Long-term debt, net	3,358.6
Total liabilities	$	7,925.1
Total purchase price	$	6,975.7

Impact of Merger

The impact of Great Plains Energy's subsidiaries on Evergy's revenues in the consolidated statements of income for the three months ended and year to date September 30, 2018 was an increase of $817.6 million and $1,060.2 million, respectively. The impact of Great Plains Energy's subsidiaries on Evergy's net income attributable to Evergy in the consolidated statements of income for the three months ended and year to date September 30, 2018 was an increase of $178.8 million and $239.0 million, respectively.

Evergy has incurred total merger-related costs, including reductions of revenue for customer bill credits, of $10.3 million and $134.3 million for the three months ended and year to date September 30, 2018, respectively, and $7.9 million and $8.9 million for the three months ended and year to date September 30, 2017, respectively.

Pro Forma Financial Information

The following unaudited pro forma financial information reflects the consolidated results of operations of Evergy as if the merger transactions had taken place on January 1, 2017. The unaudited pro forma information was calculated after applying Evergy's accounting policies and adjusting Great Plains Energy's results to reflect purchase accounting adjustments.

The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Evergy.



	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
	(millions, except per share amounts)
Operating revenues	$	1,582.5	$	1,651.5	$	4,134.8	$	4,086.7
Net income attributable to Evergy, Inc.	360.2		321.8		694.5		543.3
Basic earnings per common share	$	1.34	$	1.19	$	2.56	$	2.00
Diluted earnings per common share	$	1.34	$	1.19	$	2.55	$	2.00

Evergy, Westar Energy and Great Plains Energy incurred non-recurring costs directly related to the merger that have been excluded in the pro forma earnings presented above. After-tax non-recurring merger-related costs incurred by Evergy, Westar Energy and Great Plains Energy were $5.2 million and $73.4 million for the three months ended and year to date September 30, 2018, respectively, and $6.0 million and $9.4 million for the three months ended and year to date September 30, 2017, respectively.

Revenue

9 Months Ended

Sep. 30, 2018

Revenue from Contract with Customer [Abstract]

Revenue

3. REVENUE

Evergy's, Westar Energy's and KCP&L's revenues disaggregated by customer class are summarized in the following tables.



Three Months Ended September 30, 2018	Evergy		Westar Energy		KCP&L
Revenues	(millions)
Residential	$	647.1	$	270.5	$	243.5
Commercial	530.5		217.4		231.1
Industrial	173.4		111.9		39.1
Other retail	10.9		5.4		2.7
Total electric retail	$	1,361.9	$	605.2	$	516.4
Wholesale	118.5		82.4		29.9
Transmission	80.6		72.2		3.8
Industrial steam and other	6.0		1.5		0.7
Total revenue from contracts with customers	$	1,567.0	$	761.3	$	550.8
Other	15.5		3.5		8.8
Operating revenues	$	1,582.5	$	764.8	$	559.6

Year to Date September 30, 2018	Evergy		Westar Energy		KCP&L^(a)
Revenues	(millions)
Residential	$	1,169.4	$	671.9	$	585.4
Commercial	945.0		542.8		609.2
Industrial	375.5		297.2		105.4
Other retail	21.5		15.3		7.7
Total electric retail	$	2,511.4	$	1,527.2	$	1,307.7
Wholesale	302.4		263.7		38.5
Transmission	227.6		216.3		11.0
Industrial steam and other	10.0		4.6		3.0
Total revenue from contracts with customers	$	3,051.4	$	2,011.8	$	1,360.2
Other	24.7		4.1		48.7
Operating revenues	$	3,076.1	$	2,015.9	$	1,408.9

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Retail Revenues

The Evergy Companies' retail revenues are generated by the regulated sale of electricity to their residential, commercial and industrial customers within their franchised service territories. The Evergy Companies recognize revenue on the sale of electricity to their customers over time as the service is provided in the amount they have a right to invoice. Retail customers are billed on a monthly basis at the tariff rates approved by the KCC and MPSC based on customer kWh usage.

Revenues recorded include electric services provided but not yet billed by the Evergy Companies. Unbilled revenues are recorded for kWh usage in the period following the customers' billing cycle to the end of the month. This estimate is based on net system kWh usage less actual billed kWhs. The Evergy Companies' estimated unbilled kWhs are allocated and priced by regulatory jurisdiction across the rate classes based on actual billing rates.

The Evergy Companies also collect sales taxes and franchise fees from customers concurrent with revenue-producing activities that are levied by state and local governments. These items are excluded from revenue, and thus not reflected on the statements of income and comprehensive income, for Evergy, Westar Energy and KCP&L. Prior to the adoption of ASC 606, KCP&L recorded sales taxes and franchise fees collected from its Missouri customers gross on KCP&L's statements of comprehensive income within operating revenues and taxes other than income taxes.

Wholesale Revenues

The Evergy Companies' wholesale revenues are generated by the sale of wholesale power and capacity in circumstances when the power that the Evergy Companies generate is not required for customers in their service territory. These sales primarily occur within the SPP Integrated Marketplace. The Evergy Companies also purchase power from the SPP Integrated Marketplace and record sale and purchase activity on a net basis in wholesale revenue or fuel and purchased power expense. In addition, the Evergy Companies sell wholesale power and capacity through bilateral contracts to other counterparties, such as electric cooperatives, municipalities and other electric utilities.

For both wholesale sales to the SPP Integrated Marketplace and through bilateral contracts, the Evergy Companies recognize revenue on the sale of wholesale electricity to their customers over time as the service is provided in the amount they have a right to invoice.

With regards to the SPP Integrated Marketplace, wholesale sales are billed weekly based on the fixed transaction price determined by the market at the time of the sale and the MWh quantity purchased. With regards to bilateral contracts, wholesale sales are billed monthly based on the contractually determined transaction price and the kWh quantity purchased.

Transmission Revenues

The Evergy Companies' transmission revenues are generated by the use of their transmission networks by the SPP, which the Evergy Companies allow the SPP to access and operate on their behalf and the behalf of other SPP participants. As new transmission lines are constructed, they are included in the transmission network available to the SPP. In exchange for providing access, the SPP pays the Evergy Companies consideration determined by formula rates approved by FERC, which include the cost to construct and maintain the transmission lines and a return on investment. The price for access to the Evergy Companies' transmission networks are updated annually based on projected costs. Projections are updated to actual costs and the difference is included in subsequent year's prices.

The Evergy Companies have different treatment for their legacy transmission facilities within the SPP, which results in different levels of transmission revenue being received from the SPP. Westar Energy's transmission revenues from SPP include amounts that Westar Energy pays to the SPP on behalf of its retail electric customers for the use of Westar Energy's legacy transmission facilities. These transmission revenues are mostly offset by SPP network transmission cost expense that Westar Energy pays on behalf of its retail customers. KCP&L and GMO do not pay the SPP for their retail customers’ use of the KCP&L and GMO legacy transmission facilities and correspondingly, their transmission revenues also do not reflect the associated transmission revenue from the SPP.

The Evergy Companies recognize revenue on the sale of transmission service to their customers over time as the service is provided in the amount they have a right to invoice. Transmission service to the SPP is billed monthly based on a fixed transaction price determined by FERC formula transmission rates along with other SPP-specific charges and the MW quantity purchased.

Industrial Steam and Other Revenues

Evergy's industrial steam and other revenues are primarily generated by the regulated sale of industrial steam to GMO's steam customers. Evergy recognizes revenue on the sale of industrial steam to its customers over time as the service is provided in the amount that it has the right to invoice. Steam customers are billed on a monthly basis at the tariff rate approved by the MPSC based on customer MMBtu usage.

Optional Exemption

Evergy, Westar Energy and KCP&L do not disclose the value of unsatisfied performance obligations on certain bilateral wholesale contracts with an original expected duration of greater than one year for which they recognize revenue in the amount they have the right to invoice.

Receivables

9 Months Ended

Sep. 30, 2018

Receivables [Abstract]

Receivables

4. RECEIVABLES

The Evergy Companies' receivables are detailed in the following table.



	September 30				December 31
		2018				2017
Evergy		(millions)
Customer accounts receivable - billed		$	231.7			$	165.4
Customer accounts receivable - unbilled		191.1				76.6
Other receivables		82.4				55.4
Allowance for doubtful accounts		(8.7		)		(6.7		)
Total		$	496.5			$	290.7
Westar Energy
Customer accounts receivable - billed		$	194.0			$	165.4
Customer accounts receivable - unbilled		96.7				76.6
Other receivables		60.7				55.4
Allowance for doubtful accounts		(3.9		)		(6.7		)
Total		$	347.5			$	290.7
KCP&L ^(a)
Customer accounts receivable - billed		$	25.3			$	1.6
Customer accounts receivable - unbilled		66.6				67.6
Other receivables		14.5				39.3
Allowance for doubtful accounts		(3.5		)		(2.2		)
Total		$	102.9			$	106.3

^(a)KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Evergy's, Westar Energy's and KCP&L's other receivables at September 30, 2018 and December 31, 2017 consisted primarily of receivables from partners in jointly-owned electric utility plants and wholesale sales receivables. As of September 30, 2018, other receivables for Evergy, Westar Energy and KCP&L included receivables from contracts with customers of $57.7 million, $52.8 million and $1.0 million, respectively.

The Evergy Companies recorded bad debt expense related to contracts with customers as summarized in the following table.



	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
	(millions)
Evergy	$	4.5	$	2.0	$	10.6	$	5.4
Westar Energy	1.1		2.0		6.2		5.4
KCP&L ^(a)	3.9		2.8		7.5		6.0

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Sale of Accounts Receivable – KCP&L and GMO

KCP&L and GMO sell all of their retail electric accounts receivable to their wholly-owned subsidiaries, KCP&L Receivables Company and GMO Receivables Company, respectively, which in turn sell an undivided percentage ownership interest in the accounts receivable to Victory Receivables Corporation, an independent outside investor. Each of KCP&L Receivables Company's and GMO Receivables Company's sale of the undivided percentage ownership interest in accounts receivable to Victory Receivables Corporation is accounted for as a secured borrowing with accounts receivable pledged as collateral and a corresponding short-term collateralized note payable recognized on the balance sheets. At September 30, 2018, Evergy's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $195.0 million. At September 30, 2018 and December 31, 2017, KCP&L's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $130.0 million. KCP&L's receivable sale facility expires in September 2019 and allows for $130.0 million in aggregate outstanding principal amount of borrowings at any time. GMO's receivable sale facility expires in September 2019 and allows for $50.0 million in aggregate outstanding principal amount of borrowings from mid-November through mid-June and then $65.0 million from mid-June through mid-November.

Rate Matters and Regulation	9 Months Ended
Rate Matters and Regulation	Sep. 30, 2018
Regulated Operations [Abstract]
Rate Matters and Regulation	5. RATE MATTERS AND REGULATION KCC Proceedings Westar Energy 2018 Transmission Delivery Charge In March 2018, the KCC issued an order adjusting Westar Energy's retail prices to include updated transmission costs as reflected in the FERC transmission formula rate (TFR). The new prices were effective in April 2018 and are expected to increase Westar Energy's annual retail revenues by $31.5 million. In August 2018, Westar Energy filed an updated Transmission Delivery Charge (TDC) tariff with the KCC to reflect the reduction in revenue requirement that occurred as a result of the Tax Cuts and Jobs Act. The updated filing requested new prices decreasing Westar Energy's annual retail revenues by approximately $20 million. In October 2018, the KCC issued an order approving the request with the new prices effective October 30, 2018. Westar Energy 2018 Rate Case Proceedings In February 2018, Westar Energy filed an application with the KCC to request a two-step change in rates, a decrease to retail revenues of approximately $2 million in September 2018 followed by an increase in retail revenues of approximately $54 million in February 2019, with a return on equity of 9.85% and a rate-making equity ratio of 51.6%. The request reflects costs associated with the completion of the Western Plains Wind Farm, the expiration of wholesale contracts currently reflected in retail prices as offsets to retail cost of service, the expiration of production tax credits from prior wind investments and an updated depreciation study, partially offset by the impact of the Tax Cuts and Jobs Act and a portion of the savings from the merger with Great Plains Energy. In June 2018, Westar Energy, the KCC staff and several other intervenors in the case reached a non-unanimous stipulation and agreement to settle all outstanding issues in the case. The stipulation and agreement provides for a decrease to retail revenues of $66.0 million, before rebasing property tax expense, with a return on equity of 9.3%, a rate-making equity ratio of 51.46% and does not include a second step revenue requirement change as included in Westar Energy's initial application. The stipulation and agreement also provides for an approximately $16 million increase associated with rebasing property tax expense, an approximately $46 million increase in depreciation expense, allows for the recovery of an approximately $41 million wholesale contract that expires in 2019 through Westar Energy's fuel recovery mechanism and reflects customer benefits related to the impacts of the Tax Cuts and Jobs Act, including a one-time bill credit of approximately $50 million to be provided to customers following the conclusion of the rate case. In September 2018, the KCC issued an order approving the non-unanimous stipulation and agreement. The rates established by the order took effect on September 27, 2018. KCP&L 2018 Rate Case Proceedings In May 2018, KCP&L filed an application with the KCC to request an increase to its retail revenues of $26.2 million before rebasing property tax expense, with a return on equity of 9.85% and a rate-making equity ratio of 49.8%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs. KCP&L also requested an additional $6.7 million increase associated with rebasing property tax expense. In October 2018, KCP&L, the KCC staff and other intervenors reached a unanimous settlement agreement to settle all outstanding issues in the case. The settlement agreement provides for a decrease to retail revenues of $10.7 million before rebasing property tax expense, with a return on equity of 9.3%, a rate-making equity ratio of 49.09% and a one-time bill credit of $36.9 million for customer benefits related to the impacts of the Tax Cuts and Jobs Act. The unanimous settlement agreement is subject to the approval of the KCC. The new rates are expected to go into effect in December 2018. MPSC Proceedings KCP&L 2018 Rate Case Proceedings In January 2018, KCP&L filed an application with the MPSC to request an increase to its retail revenues of $8.9 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 50.03%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs, transmission related costs and property tax costs. KCP&L also requested an additional $7.5 million increase associated with rebasing fuel and purchased power expense. In September 2018, KCP&L, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $21.1 million and a one-time customer benefit of $38.7 million related to the impact of the Tax Cuts and Jobs Act, which will be offset against existing KCP&L regulatory assets. The final amount of the one-time customer benefit related to the impact of the Tax Cuts and Jobs Act is dependent on the effective date of new rates. In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order are expected to take effect no later than December 2018. GMO 2018 Rate Case Proceedings In January 2018, GMO filed an application with the MPSC to request a decrease to its retail revenues of $2.4 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 54.4%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs and transmission related costs. GMO also requested a $21.7 million increase associated with rebasing fuel and purchased power expense. In September 2018, GMO, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $24.0 million and a one-time bill credit of $29.3 million for customer benefits related to the impacts of the Tax Cuts and Jobs Act. The final amount of the one-time customer bill credit related to the impact of the Tax Cuts and Jobs Act is dependent on the effective date of new rates. In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order are expected to take effect no later than December 2018. FERC Proceedings Westar Energy's TFR, effective in January 2018, includes projected 2018 transmission capital expenditures and operating costs and was expected to increase annual transmission revenues by $25.5 million. Due to the passage of the Tax Cuts and Jobs Act, Westar Energy requested permission from FERC to retroactively reflect the reduction in the federal corporate income tax rate in its 2018 prices. In April 2018, FERC granted the request and Westar Energy has recorded a regulatory liability as of September 30, 2018 of $5.9 million related to this request. It is estimated the revised TFR will increase 2018 revenues by $2.3 million when compared to 2017. Westar Energy's TFR, effective in January 2019, includes projected 2019 transmission capital expenditures and operating costs and is expected to decrease annual transmission revenues by $11.2 million when compared to 2018.

Asset Retirement Obligations

9 Months Ended

Sep. 30, 2018

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

6. ASSET RETIREMENT OBLIGATIONS

Asset Retirement Obligations (AROs) associated with tangible long-lived assets are legal obligations that exist under enacted laws, statutes and written or oral contracts, including obligations arising under the doctrine of promissory estoppel. These liabilities are recognized at estimated fair value as incurred with a corresponding amount capitalized as part of the cost of the related long-lived assets and depreciated over their useful lives. Accretion of the liabilities due to the passage of time is recorded to a regulatory asset and/or liability. Changes in the estimated fair values of the liabilities are recognized when known. Evergy, Westar Energy and KCP&L record the current portion of AROs within other current liabilities on their consolidated balance sheets.

Westar Energy, KCP&L and GMO have AROs related to asbestos abatement and the closure and post-closure care of ponds and landfills containing coal combustion residuals (CCRs). In addition, Westar Energy and KCP&L have AROs related to decommissioning Wolf Creek Generating Station (Wolf Creek) and the retirement of wind generation facilities.

Certain of the Evergy Companies' generating stations or other facilities may contain asbestos due to the age of the facilities, but no confirmation or measurement of the total amount of asbestos could be determined as of September 30, 2018. Due to the inability to reasonably estimate the quantities or the amount of disturbance that will be necessary during dismantlement at the end of the life of a plant or facility, the fair value of this ARO cannot be reasonably estimated at this time. Management will continue to monitor the obligation and will recognize a liability in the period in which sufficient information becomes available to reasonably estimate its fair value.

The following table summarizes the change in the Evergy Companies' AROs for the periods ending September 30, 2018 and December 31, 2017.



	Evergy						Westar Energy						KCP&L^(a)
	2018			2017			2018			2017			2018			2017
	(millions)
Beginning balance, January 1	$	405.1		$	324.0		$	405.1		$	324.0		$	266.3		$	278.0
Liabilities assumed upon merger with Great Plains Energy	412.2			—			—			—			—			—
Liabilities incurred during the year	7.4			13.5			7.4			13.5			—			—
Revision in timing and/or estimates	(138.6		)	66.8			(133.0		)	66.8			(5.7		)	0.3
Settlements	(15.9		)	(16.0		)	(10.6		)	(16.0		)	(9.9		)	(25.5		)
Accretion	22.1			16.8			14.0			16.8			12.6			13.5
Ending balance	$	692.3		$	405.1		$	282.9		$	405.1		$	263.3		$	266.3
Less: current portion	(69.6		)	(25.1		)	(25.1		)	(25.1		)	(40.6		)	(34.9		)
Total noncurrent asset retirement obligation	$	622.7		$	380.0		$	257.8		$	380.0		$	222.7		$	231.4

^(a)KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

See Note 2 for more information regarding KCP&L's and GMO's ARO liabilities that Evergy assumed as a result of the merger.

In June 2018, Evergy and Westar Energy recorded a $127.0 million revision in estimate primarily related to Westar Energy's ARO to decommission its 47% ownership share of Wolf Creek.

Pension Plans and Other Employee Benefits

9 Months Ended

Sep. 30, 2018

Retirement Benefits [Abstract]

Pension Plans and Other Employee Benefits

7. PENSION PLANS AND OTHER EMPLOYEE BENEFITS

Evergy and certain of its subsidiaries maintain, and Westar Energy and KCP&L participate in, qualified non-contributory defined benefit pension plans covering the majority of Westar Energy's and KCP&L's employees as well as certain non-qualified plans covering certain active and retired officers. Evergy is also responsible for its 94% share of Wolf Creek Nuclear Operating Corporation (WCNOC) defined benefit plans, consisting of Westar Energy's and KCP&L's respective 47% shares.

For the majority of employees, pension benefits under these plans reflect the employees' compensation, years of service and age at retirement. However, for the plan covering Westar Energy's employees, the benefits for non-union employees hired between 2002 and the second quarter of 2018 and union employees hired beginning in 2012 are derived from a cash balance account formula. For the plans covering KCP&L's employees, the benefits for union employees hired beginning in 2014 are derived from a cash balance account formula and the plans were closed to future non-union employees in 2014.

Evergy and its subsidiaries also provide certain post-retirement health care and life insurance benefits for substantially all retired employees of Westar Energy and KCP&L and their respective shares of WCNOC's post-retirement benefit plans.

The Evergy Companies record pension and post-retirement expense in accordance with rate orders from the KCC and MPSC that allow the difference between pension and post-retirement costs under GAAP and costs for ratemaking to be recognized as a regulatory asset or liability. This difference between financial and regulatory accounting methods is due to timing and will be eliminated over the life of the plans.

The following tables provide the components of net periodic benefit costs prior to the effects of capitalization and sharing with joint owners of power plants.



	Pension Benefits									Post-Retirement Benefits
Three Months Ended September 30, 2018	Evergy			Westar Energy			KCP&L			Evergy			Westar Energy			KCP&L
Components of net periodic benefit costs	(millions)
Service cost	$	20.2		$	8.0		$	9.1		$	0.7		$	0.4		$	0.4
Interest cost	26.3			12.7			9.4			2.5			1.2			0.8
Expected return on plan assets	(27.0		)	(13.9		)	(10.6		)	(2.5		)	(1.8		)	(0.4		)
Amortization of unrecognized:
Prior service cost	0.3			0.2			0.2			0.1			0.1			—
Recognized net actuarial (gain)/loss	8.1			8.1			8.4			(0.1		)	(0.1		)	—
Net periodic benefit costs before regulatory adjustment	27.9			15.1			16.5			0.7			(0.2		)	0.8
Regulatory adjustment	2.6			2.8			0.7			(0.4		)	(0.4		)	0.1
Net periodic benefit costs	$	30.5		$	17.9		$	17.2		$	0.3		$	(0.6	)	$	0.9

	Pension Benefits									Post-Retirement Benefits
Year to Date September 30, 2018	Evergy			Westar Energy			KCP&L^(a)			Evergy			Westar Energy			KCP&L^(a)
Components of net periodic benefit costs	(millions)
Service cost	$	40.4		$	24.1		$	27.4		$	1.5		$	1.0		$	1.1
Interest cost	56.2			38.1			28.3			5.4			3.7			2.5
Expected return on plan assets	(59.3		)	(41.9		)	(31.7		)	(6.2		)	(5.2		)	(1.4		)
Amortization of unrecognized:
Prior service cost	0.6			0.5			0.4			0.3			0.3			—
Recognized net actuarial (gain)/loss	24.4			24.4			25.1			(0.4		)	(0.4		)	(0.1		)
Net periodic benefit costs before regulatory adjustment	62.3			45.2			49.5			0.6			(0.6		)	2.1
Regulatory adjustment	8.4			8.4			2.1			(1.3		)	(1.3		)	(0.2		)
Net periodic benefit costs	$	70.7		$	53.6		$	51.6		$	(0.7	)	$	(1.9	)	$	1.9

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.



	Pension Benefits									Post-Retirement Benefits
Three Months Ended September 30, 2017	Evergy			Westar Energy			KCP&L^(a)			Evergy			Westar Energy			KCP&L^(a)
Components of net periodic benefit costs	(millions)
Service cost	$	7.2		$	7.2		$	8.1		$	0.3		$	0.3		$	0.4
Interest cost	13.1			13.1			9.8			1.4			1.4			0.9
Expected return on plan assets	(13.4		)	(13.4		)	(9.5		)	(1.8		)	(1.8		)	(0.4		)
Amortization of unrecognized:
Prior service cost	0.1			0.1			0.2			0.1			0.1			—
Recognized net actuarial (gain)/loss	6.7			6.7			8.9			(0.2		)	(0.2		)	(0.1		)
Net periodic benefit costs before regulatory adjustment	13.7			13.7			17.5			(0.2		)	(0.2		)	0.8
Regulatory adjustment	3.6			3.6			0.2			(0.4		)	(0.4		)	(0.1		)
Net periodic benefit costs	$	17.3		$	17.3		$	17.7		$	(0.6	)	$	(0.6	)	$	0.7
^(a)KCP&L amounts are not included in consolidated Evergy for the three months ended September 30, 2017.

	Pension Benefits									Post-Retirement Benefits
Year to Date September 30, 2017	Evergy			Westar Energy			KCP&L^(a)			Evergy			Westar Energy			KCP&L^(a)
Components of net periodic benefit costs	(millions)
Service cost	$	21.5		$	21.5		$	24.4		$	0.9		$	0.9		$	1.1
Interest cost	39.3			39.3			29.4			4.2			4.2			2.8
Expected return on plan assets	(40.2		)	(40.2		)	(28.6		)	(5.2		)	(5.2		)	(1.3		)
Amortization of unrecognized:
Prior service cost	0.5			0.5			0.4			0.3			0.3			—
Recognized net actuarial (gain)/loss	20.2			20.2			26.7			(0.6		)	(0.6		)	(0.3		)
Net periodic benefit costs before regulatory adjustment	41.3			41.3			52.3			(0.4		)	(0.4		)	2.3
Regulatory adjustment	10.6			10.6			4.3			(1.4		)	(1.4		)	0.9
Net periodic benefit costs	$	51.9		$	51.9		$	56.6		$	(1.8	)	$	(1.8	)	$	3.2

^(a)KCP&L amounts are not included in consolidated Evergy for year to date September 30, 2017.

The components of net periodic benefit costs other than the service cost component are included in other expense on the Evergy Companies' consolidated statements of income and comprehensive income.

Year to date September 30, 2018, Evergy, Westar Energy and KCP&L made pension contributions of $53.1 million, $43.1 million and $23.7 million, respectively. Evergy's year to date September 30, 2018 pension contributions consist of Westar Energy's year to date September 30, 2018 contributions and KCP&L's contributions made following the closing of the merger in June 2018.

Evergy expects to make additional pension contributions of $66.3 million in 2018 to satisfy the Employee Retirement Income Security Act of 1974, as amended (ERISA) funding requirements and KCC and MPSC rate orders, of which $4.9 million is expected to be paid by Westar Energy and $61.4 million is expected to be paid by KCP&L. Also in 2018, Evergy and KCP&L expect to make contributions of $4.6 million to the post-retirement benefit plans.

Equity Compensation

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Equity Compensation

8. EQUITY COMPENSATION

Upon the consummation of the merger, Evergy assumed both Westar Energy's Long-Term Incentive and Share Award plan (LTISA) and Great Plains Energy's Amended Long-Term Incentive Plan, which was renamed the Evergy, Inc. Long-Term Incentive Plan. All outstanding share-based payment awards under Westar Energy's LTISA vested at the closing of the merger transaction and were converted into a right to receive Evergy common stock with the exception of certain RSUs issued prior to the closing of the merger to certain officers and employees of Westar Energy. The vesting of these shares resulted in the recognition of $14.6 million of compensation expense in Evergy's and Westar Energy's consolidated statements of income for year to date September 30, 2018.

All of Great Plains Energy's outstanding performance shares, restricted stock, RSUs and director deferred share units under Great Plains Energy's Amended Long-Term Incentive Plan were converted into equivalent Evergy performance shares, restricted stock, RSUs and director deferred share units at Great Plains Energy's merger exchange ratio of 0.5981. The estimated fair value of these converted awards that was allocated to the purchase price was $12.5 million, after-tax. See Note 2 for more information regarding the merger.

The following table summarizes the Evergy Companies' equity compensation expense and the associated income tax (expense) benefit.



	Three Months Ended September 30					Year to Date September 30
	Three Months Ended September 30					Year to Date September 30
	2018			2017		2018			2017
Evergy	(millions)
Equity compensation expense	$	4.3		$	2.1	$	26.0		$	6.7
Income tax (expense) benefit	(1.5		)	0.8		1.9			2.6
Westar Energy
Equity compensation expense	$	2.0		$	2.1	$	22.6		$	6.7
Income tax (expense) benefit	(1.0		)	0.8		2.1			2.6
KCP&L^(a)
Equity compensation expense	$	1.6		$	1.2	$	4.8		$	2.9
Income tax (expense) benefit	(0.7		)	0.4		(0.1		)	1.2

^(a)KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Performance Shares

The vesting of performance shares is contingent upon achievement of specific performance goals over a stated period of time as approved by the Compensation and Leadership Development Committee of the Evergy Board. The number of performance shares ultimately vested can vary from the number of shares initially granted depending on either Great Plains Energy's performance prior to the closing of the merger transaction or Evergy's performance based on the stated performance period of the awards. Compensation expense for performance shares is calculated by recognizing the portion of the grant date fair value for each reporting period for which the requisite service has been rendered. Dividends are accrued over the vesting period and paid in cash based on the number of performance shares ultimately paid.

The fair value of the converted Great Plains Energy performance share awards was estimated using the market value of Westar Energy's and Great Plains Energy's common stock at the valuation date and a Monte Carlo simulation technique that incorporates assumptions for inputs of expected volatilities, dividend yield and risk-free rates. Expected volatility is based on daily stock price change based on historical common stock information during a historical period commensurate with the remaining term of the performance period of the grant. The risk-free rate is based upon the rate at the time of the evaluation for zero-coupon government bonds with a maturity consistent with the remaining performance period of the grant. The dividend yield is based on the most recent dividends paid by Westar Energy, as Evergy's stock price assumes Westar Energy's stock price on a forward basis, and the grant date stock price on the valuation date. For the Great Plains Energy performance shares converted into Evergy awards upon the closing of the merger, inputs for expected volatility, dividend yield, and risk-free rates were 16.6% - 18.5% , 2.96% and 1.8% - 2.6%, respectively. Evergy and Westar Energy did not have any performance share awards issued and outstanding prior to the close of the merger.

Performance share activity for year to date September 30, 2018 is summarized in the following table.



	Performance Shares			Grant Date Fair Value*
Beginning balance January 1, 2018		—			$	—
Converted Great Plains Energy awards upon merger		351,708			63.79
Forfeited		(3,212	)		63.44
Ending balance September 30, 2018		348,496			63.80

* weighted-average

At September 30, 2018, the remaining weighted-average contractual term was 1.3 years. There were no shares granted for the three months ended September 30, 2018 and 2017, respectively. The weighted-average grant-date fair value of shares granted was $63.79 year to date September 30, 2018. At September 30, 2018, there was $10.6 million of total unrecognized compensation expense, net of forfeiture rates, related to converted Great Plains Energy performance shares granted under its Amended Long-Term Incentive Plan, which will be recognized over the remaining weighted-average contractual term.

Restricted Stock

Restricted stock cannot be sold or otherwise transferred by the recipient prior to vesting and has a value equal to the fair market value of the shares on the issue date. Restricted stock shares vest over a stated period of time with accruing reinvested dividends subject to the same restrictions. Compensation expense, calculated by multiplying shares by the grant-date fair value related to restricted stock, is recognized on a straight-line basis over the requisite service period of the award. Evergy and Westar Energy did not have any restricted stock awards issued and outstanding prior to the close of the merger.

Restricted stock activity for year to date September 30, 2018 is summarized in the following table.



	Nonvested Restricted Stock			Grant Date Fair Value*
Beginning balance January 1, 2018		—			$	—
Converted Great Plains Energy awards upon merger		122,505			54.05
Vested		(4,222	)		54.50
Forfeited		(1,070	)		54.04
Ending balance September 30, 2018		117,213			54.03

* weighted-average

At September 30, 2018, the remaining weighted-average contractual term was 1.4 years. There were no shares granted for the three months ended September 30, 2018 and 2017, respectively. The weighted-average grant-date fair value of shares granted was $54.05 year to date September 30, 2018. At September 30, 2018, there was $3.1 million of total unrecognized compensation expense, net of forfeiture rates, related to converted Great Plains Energy restricted stock granted under its Amended Long-Term Incentive Plan, which will be recognized over the remaining weighted-average contractual term. The total fair value of shares vested was $0.2 million for the three months ended and year to date September 30, 2018.

Restricted Share Units

Evergy and Westar Energy have historically used RSUs for their stock-based compensation awards. RSU awards are grants that entitle the holder to receive shares of common stock as the awards vest. These RSU awards are defined as nonvested shares and do not include restrictions once the awards have vested. These RSUs have either taken the form of RSUs with only service requirements that vest solely upon the passage of time or RSUs with performance measures that vest upon expiration of the award term. All issued and outstanding Evergy and Westar Energy RSU awards with performance measures vested in connection with the closing of the merger transaction in June 2018.

Evergy measures the fair value of RSUs with only service requirements based on the fair market value of the underlying common stock as of the grant date. RSU awards with only service conditions recognize compensation expense by multiplying shares by the grant-date fair value related to the RSU and recognizing it on a straight-line basis over the requisite service period for the entire award, including for those RSUs that have a graded vesting schedule. Nonforfeitable dividend equivalents, or the rights to receive cash equal to the value of dividends paid on Evergy's common stock, are paid on certain of these RSUs during the vesting period. Nonforfeitable dividends equivalents are recorded directly to retained earnings.

RSU activity for awards with only service requirements for year to date September 30, 2018 is summarized in the following table.



	Nonvested Restricted Share Units			Grant Date Fair Value*
Beginning balance January 1, 2018		255,964			$	46.09
Granted		222,465			52.16
Converted Great Plains Energy awards upon merger		82,331			53.77
Vested		(342,599	)		46.81
Forfeited		(905	)		50.73
Ending balance September 30, 2018		217,256			54.07

* weighted-average

At September 30, 2018, the remaining weighted-average contractual term related to RSU awards with only service requirements was 1.7 years. There were no RSUs granted for the three months ended September 30, 2018 and 2017, respectively. The weighted-average grant-date fair value of RSUs granted with only service requirements was $52.16 and $53.25 year to date September 30, 2018, and 2017, respectively. At September 30, 2018, there was $9.5 million of unrecognized compensation expense related to unvested RSUs. There were no RSUs with only service requirements that vested for the three months ended September 30, 2018. The total fair value of RSUs with only service requirements that vested year to date September 30, 2018 was $16.0 million. The total fair value of RSUs with only service requirements that vested for the three months ended and year to date September 30, 2017 was $0.2 million and $3.8 million, respectively.

Short-term Borrowings and Short-term Bank Lines of Credit

9 Months Ended

Sep. 30, 2018

Short-term Borrowings and Short-term Bank Lines of Credit [Abstract]

Short-term Borrowings and Short-term Bank Lines of Credit

9. SHORT-TERM BORROWINGS AND SHORT-TERM BANK LINES OF CREDIT

In September 2018, Evergy entered into a $2.5 billion master credit facility which expires in 2023. Evergy, Westar Energy, KCP&L and GMO have borrowing capacity under the master credit facility with specific sublimits for each borrower. These sublimits can be unilaterally adjusted by Evergy for each borrower provided the sublimits remain within minimum and maximum sublimits as specified in the facility. A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times. As of September 30, 2018, Evergy, Westar Energy, KCP&L and GMO were in compliance with this covenant.

In connection with the entry into the master credit facility, each of Evergy (as successor to Great Plains Energy), Westar Energy, KCP&L and GMO terminated its existing credit facilities in September 2018.

The following table summarizes the committed credit facilities (excluding receivable sale facilities) available to the Evergy Companies as of September 30, 2018 and December 31, 2017.



			Amounts Drawn
	Credit Facility		Commercial Paper		Letters of Credit		Cash Borrowings		Available Borrowings		Weighted Average Interest Rate on Short-Term Borrowings
September 30, 2018	(millions)
Evergy, Inc.	$	450.0	n/a		$	1.0	$	—	$	449.0	—%
Westar Energy	1,000.0		326.3		18.3		—		655.4		2.42%
KCP&L	600.0		209.2		2.7		—		388.1		2.50%
GMO	450.0		140.4		2.1		—		307.5		2.46%
Evergy	$	2,500.0	$	675.9	$	24.1	$	—	$	1,800.0

December 31, 2017
Westar Energy^(b)	$	979.3	$	275.7	$	11.8	$	—	$	691.8	1.83%
KCP&L^(a)	600.0		167.5		2.7		—		429.8		1.95%
Evergy	979.3		275.7		11.8		—		691.8		1.83%

^(a)KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

^(b)$20.7 million of Westar Energy's $730.0 million and $270.0 million revolving credit facilities expired in September 2017.

Long-Term Debt

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Long-Term Debt

10. LONG-TERM DEBT

As of September 30, 2018, Evergy's outstanding long-term debt, including current maturities, includes $3,659.7 million related to KCP&L, GMO and the assumed long-term debt of Great Plains Energy discussed further below. This amount also includes $153.0 million of fair value adjustments recorded in connection with purchase accounting for the merger transaction, which are not part of future principal payments and will amortize over the remaining life of the associated debt instruments. See Note 2 for more information regarding the merger transaction. The series of long-term debt obligations originally issued by Great Plains Energy and assumed by Evergy, Inc. as part of the merger transaction were:


•	$350.0 million of 4.85% unsecured Senior Notes; and


•	$287.5 million of 5.292% unsecured Senior Notes.

KCP&L Senior Notes

In March 2018, KCP&L issued, at a discount, $300.0 million of 4.20% unsecured Senior Notes, maturing in 2048. KCP&L also repaid its $350.0 million of 6.375% unsecured Senior Notes at maturity in March 2018.

KCP&L EIRR Bond Remarketing

In July 2018, KCP&L remarketed its unsecured Series 2008 Environmental Improvement Revenue Refunding (EIRR) bonds maturing in 2038 totaling $23.4 million at a fixed rate of 2.75% through June 30, 2022.

GMO Senior Notes

As a result of the consummation of the merger transaction, a change in control provision in GMO's Series A, B and C Senior Notes was triggered that allowed holders a one-time option to elect for early repayment of their notes at par value, plus accrued interest. Several holders of GMO's Series A and B Senior Notes elected this option and in July 2018, GMO redeemed $89.0 million of its Series A Senior Notes and $15.0 million of its Series B Senior Notes.

Fair Value Measurements

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

11. FAIR VALUE MEASUREMENTS

Values of Financial Instruments

GAAP establishes a hierarchical framework for disclosing the transparency of the inputs utilized in measuring assets and liabilities at fair value. Management's assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the classification of assets and liabilities within the fair value hierarchy levels. In addition, the Evergy Companies measure certain investments that do not have a readily determinable fair value at net asset value (NAV), which are not included in the fair value hierarchy. Further explanation of these levels and NAV is summarized below.

Level 1 – Quoted prices are available in active markets for identical assets or liabilities. The types of assets and liabilities include in Level 1 are highly liquid and actively traded instruments with quoted prices, such as equities listed on public exchanges.

Level 2 – Pricing inputs are not quoted prices in active markets, but are either directly or indirectly observable. The types of assets and liabilities included in Level 2 are certain marketable debt securities, financial instruments traded in less than active markets or other financial instruments priced with models using highly observable inputs.

Level 3 – Significant inputs to pricing have little or no transparency. The types of assets and liabilities included in Level 3 are those with inputs requiring significant management judgment or estimation.

NAV - Investments that do not have a readily determinable fair value are measured at NAV. These investments do not consider the observability of inputs and, therefore, they are not included within the fair value hierarchy. The Evergy Companies include in this category investments in private equity, real estate and alternative investment funds that do not have a readily determinable fair value. The underlying alternative investments include collateralized debt obligations, mezzanine debt and a variety of other investments.

The Evergy Companies record cash and cash equivalents, accounts receivable and short-term borrowings on their consolidated balance sheets at cost, which approximates fair value due to the short-term nature of these instruments.

The Evergy Companies measure the fair value of long-term debt using Level 2 measurements available as of the measurement date. The book value and fair value of the Evergy Companies' long-term debt and long-term debt of variable interest entities is summarized in the following table.



	September 30, 2018				December 31, 2017
	Book Value		Fair Value		Book Value		Fair Value
Long-term debt^(a)	(millions)
Evergy^(b)	$	7,349.4	$	7,362.2	$	3,687.6	$	4,010.6
Westar Energy	3,689.7		3,750.8		3,687.6		4,010.6
KCP&L^(c)	2,529.9		2,611.3		2,582.2		2,799.1
Long-term debt of variable interest entities^(a)
Evergy	$	81.4	$	80.7	$	109.9	$	110.8
Westar Energy	81.4		80.7		109.9		110.8

^(a)Includes current maturities.

^(b)Book value as of September 30, 2018 includes $153.0 million of fair value adjustments recorded in connection with purchase accounting for the Great Plains Energy and Westar Energy merger, which are not part of future principal payments and will amortize over the remaining life of the associated debt instrument. See Note 2 for more information regarding the merger transaction.

^(c)KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Recurring Fair Value Measurements

The following tables include the Evergy Companies' balances of financial assets and liabilities measured at fair value on a recurring basis.



Description	September 30 2018			Level 1		Level 2			Level 3			NAV
Westar Energy		(millions)
Assets
Nuclear decommissioning trust^(a)
Domestic equity funds		$	80.9	$	74.7		$	—		$	—		$	6.2
International equity funds		42.3		42.3			—			—			—
Core bond fund		36.8		36.8			—			—			—
High-yield bond fund		20.1		20.1			—			—			—
Emerging markets bond fund		15.5		15.5			—			—			—
Combination debt/equity/other fund		14.8		14.8			—			—			—
Alternative investments fund		23.6		—			—			—			23.6
Real estate securities fund		11.5		—			—			—			11.5
Cash equivalents		0.3		0.3			—			—			—
Total nuclear decommissioning trust		245.8		204.5			—			—			41.3
Rabbi trust
Core bond fund		24.9		—			—			—			24.9
Combination debt/equity/other fund		6.2		—			—			—			6.2
Cash equivalents		0.1		0.1			—			—			—
Total rabbi trust		31.2		0.1			—			—			31.1
Total		$	277.0	$	204.6		$	—		$	—		$	72.4
KCP&L
Assets
Nuclear decommissioning trust^(a)
Equity securities		$	195.2	$	195.2		$	—		$	—		$	—
Debt securities
U.S. Treasury		39.5		39.5			—			—			—
U.S. Agency		0.4		—			0.4			—			—
State and local obligations		2.1		—			2.1			—			—
Corporate bonds		32.3		—			32.3			—			—
Foreign governments		0.1		—			0.1			—			—
Cash equivalents		1.5		1.5			—			—			—
Other		1.1		1.1			—			—			—
Total nuclear decommissioning trust		272.2		237.3			34.9			—			—
Self-insured health plan trust^(b)
Equity securities		0.5		0.5			—			—			—
Debt securities		3.1		0.3			2.8			—			—
Cash and cash equivalents		9.4		9.4			—			—			—
Total self-insured health plan trust		13.0		10.2			2.8			—			—
Total		$	285.2	$	247.5		$	37.7		$	—		$	—
Other Evergy
Assets
Rabbi trusts
Fixed income fund		$	13.5	$	—		$	—		$	—		$	13.5
Total rabbi trusts		$	13.5	$	—		$	—		$	—		$	13.5
Evergy
Assets
Nuclear decommissioning trust ^(a)		$	518.0	$	441.8		$	34.9		$	—		$	41.3
Rabbi trusts		44.7		0.1			—			—			44.6
Self-insured health plan trust ^(b)		13.0		10.2			2.8			—			—
Total		$	575.7	$	452.1		$	37.7		$	—		$	85.9



Description	December 31 2017			Level 1			Level 2			Level 3			NAV
Westar Energy		(millions)
Assets
Nuclear decommissioning trust^(a)(c)
Domestic equity funds		$	73.8		$	—		$	68.7		$	—		$	5.1
International equity funds		47.9			—			47.9			—			—
Core bond fund		33.3			—			33.3			—			—
High-yield bond fund		18.1			—			18.1			—			—
Emerging markets bond fund		17.3			—			17.3			—			—
Combination debt/equity/other fund		14.1			—			14.1			—			—
Alternative investments fund		21.7			—			—			—			21.7
Real estate securities fund		10.8			—			—			—			10.8
Cash equivalents		0.1			0.1			—			—			—
Total nuclear decommissioning trust		237.1			0.1			199.4			—			37.6
Rabbi trust^(c)
Core bond fund		27.3			—			27.3			—			—
Combination debt/equity/other fund		6.8			—			6.8			—			—
Cash equivalents		0.2			0.2			—			—			—
Total rabbi trust		34.3			0.2			34.1			—			—
Total		$	271.4		$	0.3		$	233.5		$	—		$	37.6
KCP&L^(d)
Assets
Nuclear decommissioning trust ^(a)
Equity securities		$	183.8		$	183.8		$	—		$	—		$	—
Debt securities
U.S. Treasury		35.3			35.3			—			—			—
U.S. Agency		0.4			—			0.4			—			—
State and local obligations		2.1			—			2.1			—			—
Corporate bonds		34.1			—			34.1			—			—
Foreign governments		0.1			—			0.1			—			—
Cash equivalents		2.5			2.5			—			—			—
Other		0.1			0.1			—			—			—
Total nuclear decommissioning trust		258.4			221.7			36.7			—			—
Self-insured health plan trust^(b)
Equity securities		0.5			0.5			—			—			—
Debt securities		2.7			0.3			2.4			—			—
Cash and cash equivalents		7.7			7.7			—			—			—
Total self-insured health plan trust		10.9			8.5			2.4			—			—
Total		$	269.3		$	230.2		$	39.1		$	—		$	—
Evergy
Assets
Nuclear decommissioning trust^(a)(c)		$	237.1		$	0.1		$	199.4		$	—		$	37.6
Rabbi trust^(c)		34.3			0.2			34.1			—			—
Total		$	271.4		$	0.3		$	233.5		$	—		$	37.6


^(a)	Fair value is based on quoted market prices of the investments held by the trust and/or valuation models.


^(b)	Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 1 are comprised of U.S. Treasury securities. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities.

^(c)

In the second quarter of 2018, Evergy and Westar Energy re-evaluated the classification, within the fair value hierarchy, of their various fund investments within both Westar Energy's nuclear decommissioning trust and rabbi trusts. As a result, Evergy and Westar Energy determined that certain fund investments within the nuclear decommissioning trust in the amount of $199.4 million as of December 31, 2017, should have been classified as Level 1, instead of Level 2. This determination is based on the fact that the fair value of these funds is based on daily published prices at which Evergy and Westar Energy are able to redeem their investments without restriction on a daily basis. Evergy and Westar Energy also determined that certain fund investments within their rabbi trusts in the amount of $34.1 million as of December 31, 2017, should have been measured using the NAV per share (or its equivalent) practical expedient, instead of as a Level 2 investment. This determination is based on the fact that these funds do not meet the definition of readily determinable fair value due to the absence of a published NAV. Evergy and Westar Energy have determined that these errors are immaterial to their current and previously filed financial reports and accordingly, have not revised prior periods but have reflected the changes in fair value hierarchy classification as of September 30, 2018.


^(d)	KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Certain Evergy and Westar Energy investments included in the table above are measured at NAV as they do not have readily determinable fair values. In certain situations, these investments may have redemption restrictions.

The following table provides additional information on these Evergy and Westar Energy investments.



	September 30, 2018				December 31, 2017				September 30, 2018
	Fair		Unfunded		Fair		Unfunded		Redemption	Length of
	Value		Commitments		Value		Commitments		Frequency	Settlement
Westar Energy	(millions)
Nuclear decommissioning trust:
Domestic equity funds	$	6.2	$	4.8	$	5.1	$	2.8	(a)	(a)
Alternative investments fund^(b)	23.6		—		21.7		—		Quarterly	65 days
Real estate securities fund^(b)	11.5		—		10.8		—		Quarterly	65 days
Total	$	41.3	$	4.8	$	37.6	$	2.8
Rabbi trust:
Core bond fund	$	24.9	$	—	$	—	$	—	(c)	(c)
Combination debt/equity/other fund	6.2		—		—		—		(c)	(c)
Total	$	31.1	$	—	$	—	$	—
Other Evergy
Rabbi trusts:
Fixed income fund^(d)	$	13.5	$	—	$	—	$	—	(c)	(c)
Total Evergy investments at NAV	$	85.9	$	4.8	$	37.6	$	2.8

^(a)

This investment is in five long-term private equity funds that do not permit early withdrawal. Investments in these funds cannot be distributed until the underlying investments have been liquidated, which may take years from the date of initial liquidation. Three funds have begun to make distributions. The initial investment in the fourth and fifth fund occurred in the second quarter of 2016 and first quarter of 2018, respectively. The fourth fund's term is 15 years, subject to the general partner's right to extend the the term for up to three additional one-year periods. The fifth fund's term will be 15 years after the initial closing date, subject to additional extensions approved by the Advisory Committee to provide for an orderly liquidation of fund investments and dissolution of the fund.


^(b)	There is a holdback on final redemptions.


^(c)	This investment can be redeemed immediately and is not subject to any restrictions on redemptions.


^(d)	This investment is recorded at GMO. GMO amounts are not included in consolidated Evergy as of December 31, 2017.

The Evergy Companies hold equity and debt investments classified as securities in various trusts including for the purposes of funding the decommissioning of Wolf Creek and for the benefit of certain retired executive officers of Westar Energy. The Evergy Companies record net realized and unrealized gains and losses on the nuclear decommissioning trusts in regulatory liabilities on their consolidated balance sheets and record net realized and unrealized gains and losses on Westar Energy's rabbi trust in the consolidated statements of income.

The following table summarizes the net unrealized gains (losses) for the Evergy Companies' nuclear decommissioning trusts and rabbi trusts.



	Three Months Ended September 30					Year to Date September 30
	2018			2017		2018			2017
Westar Energy	(millions)
Nuclear decommissioning trust - equity securities	$	6.5		$	7.7	$	(6.4	)	$	22.2
Rabbi trust	3.7			16.5		3.2			19.0
Total	$	10.2		$	24.2	$	(3.2	)	$	41.2
KCP&L^(a)
Nuclear decommissioning trust - equity securities	$	8.6		$	6.9	$	9.1		$	17.8
Nuclear decommissioning trust - debt securities	(0.5		)	—		(2.8		)	0.7
Total	$	8.1		$	6.9	$	6.3		$	18.5
Evergy
Nuclear decommissioning trust - equity securities	$	15.1		$	7.7	$	1.1		$	22.2
Nuclear decommissioning trust - debt securities	(0.5		)	—		(0.8		)	—
Rabbi trusts	3.7			16.5		3.1			19.0
Total	$	18.3		$	24.2	$	3.4		$	41.2

^(a)KCP&L amounts are only included in consolidated Evergy from the date of the merger, June 4, 2018 through September 30, 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. COMMITMENTS AND CONTINGENCIES Contractual Commitments For information regarding long-term contractual commitments, including fuel and purchased power commitments, see Note 14 of the Westar Energy 2017 Form 10-K and Note 15 of the Great Plains Energy and KCP&L combined 2017 Form 10-K. Environmental Matters Set forth below are descriptions of contingencies related to environmental matters that may impact the Evergy Companies or their financial results. Management's assessment of these contingencies, which are based on federal and state statutes and regulations, and regulatory agency and judicial interpretations and actions, has evolved over time. There are a variety of final and proposed laws and regulations that could have a material adverse effect on the Evergy Companies operations and consolidated financial results. Due in part to the complex nature of environmental laws and regulations, the Evergy Companies are unable to assess the impact of potential changes that may develop with respect to the environmental contingencies described below. Cross-State Air Pollution Update Rule In September 2016, the Environmental Protection Agency (EPA) finalized the Cross-State Air Pollution Update Rule. The final rule addresses interstate transport of nitrogen oxides emissions in 22 states including Kansas, Missouri and Oklahoma during the ozone season and the impact from the formation of ozone on downwind states with respect to the 2008 ozone National Ambient Air Quality Standards (NAAQS). Starting with the 2017 ozone season, the final rule revised the existing ozone season allowance budgets for Missouri and Oklahoma and established an ozone season budget for Kansas. In June 2018, the EPA proposed that the Cross-State Air Pollution Update Rule satisfied the "Good Neighbor" obligations for the 2008 ozone NAAQS and therefore the EPA is proposing no additional reduction in the current ozone season allowance budgets. Various states and others are challenging the Cross-State Air Pollution Update Rule in the U.S. Court of Appeals for the D.C. Circuit (D.C. Circuit) but the rule remains in effect. It is not expected that this rule will have a material impact on the Evergy Companies' operations and consolidated financial results. National Ambient Air Quality Standards Under the Clean Air Act Amendments of 1990 (Clean Air Act), the EPA sets NAAQS for certain emissions known as the “criteria pollutants” considered harmful to public health and the environment, including two classes of particulate matter (PM), ozone, nitrogen dioxide (NO₂) (a precursor to ozone), carbon monoxide and sulfur dioxide (SO₂), which result from fossil fuel combustion. Areas meeting the NAAQS are designated attainment areas while those that do not meet the NAAQS are considered nonattainment areas. Each state must develop a plan to bring nonattainment areas into compliance with the NAAQS. NAAQS must be reviewed by the EPA at five-year intervals. In October 2015, the EPA strengthened the ozone NAAQS by lowering the standards from 75 ppb to 70 ppb. In September 2016, the Kansas Department of Health & Environment (KDHE) recommended to the EPA that they designate eight counties in the state of Kansas as in attainment with the standard, and each remaining county in Kansas as attainment/unclassifiable. Also, in September 2016, the Missouri Department of Natural Resources (MDNR) recommended to the EPA that they designate all Missouri counties in KCP&L's and GMO's service territories as attainment/unclassifiable. In November 2017, the EPA designated all counties in the State of Kansas as well as the Missouri counties in KCP&L's and GMO's service territories as attainment/unclassifiable. It is not expected that this will have a material impact on the Evergy Companies' consolidated financial results. In December 2012, the EPA strengthened an existing NAAQS for one class of PM. In December 2014, the EPA designated the entire state of Kansas and those portions of Missouri served by KCP&L and GMO as attainment/unclassifiable with the standard. It is not expected that this will have a material impact on the Evergy Companies' operations or consolidated financial results. The Evergy Companies continue to communicate with their regulatory agencies regarding these standards and evaluate what impact the revised NAAQS could have on their operations and consolidated financial results. If areas surrounding the Evergy Companies' facilities are designated in the future as nonattainment and/or it is required to install additional equipment to control emissions at facilities of the Evergy Companies, it could have a material impact on the operations and consolidated financial results of the Evergy Companies. Greenhouse Gases Burning coal and other fossil fuels releases carbon dioxide (CO₂) and other gases referred to as greenhouse gases (GHG). Various regulations under the federal Clean Air Act limit CO₂ and other GHG emissions, and in addition, other measures are being imposed or offered by individual states, municipalities and regional agreements with the goal of reducing GHG emissions. In October 2015, the EPA published a rule establishing new source performance standards (NSPS) for GHGs that limit CO₂ emissions for new, modified and reconstructed coal and natural gas fueled electric generating units to various levels per MWh depending on various characteristics of the units. Legal challenges to the GHG NSPS have been filed in the D.C. Circuit by various states and industry members. Also in October 2015, the EPA published a rule establishing guidelines for states to regulate CO₂ emissions from existing power plants. The standards for existing plants are known as the Clean Power Plan (CPP). Under the CPP, interim emissions performance rates must be achieved beginning in 2022 and final emissions performance rates must be achieved by 2030. Legal challenges to the CPP were filed by groups of states and industry members, including Westar Energy, in the D.C. Circuit. The CPP was stayed by the Supreme Court in February 2016 and, accordingly, is not currently being implemented by the states. In April 2017, the EPA published in the Federal Register a notice of withdrawal of the proposed CPP federal plan, proposed model trading rules and proposed Clean Energy Incentive Program design details. Also in April 2017, the EPA published a notice in the Federal Register that it was initiating administrative reviews of the CPP and the GHG NSPS. In October 2017, the EPA issued a proposed rule to repeal the CPP. The proposed rule indicates the CPP exceeds EPA’s authority and the EPA has not determined whether they will issue a replacement rule. The EPA solicited comments on the legal interpretations contained in this rulemaking. In December 2017, the EPA issued an advance notice of proposed rulemaking to solicit feedback on specific areas of the CPP that could be changed. In August 2018, the EPA published in the Federal Register proposed regulations which contained (1) emission guidelines for GHG emissions from existing electric utility generating units (EGUs), (2) revisions to emission guideline implementing regulations and (3) revisions to the new source review (NSR) program. The proposed emission guidelines are better known as the Affordable Clean Energy (ACE) Rule. The ACE Rule would establish emission guidelines for states to use in the development of plans to reduce GHG emissions from existing coal-fired EGUs. The ACE Rule is also the replacement rule for the CPP. The ACE rule proposes to determine the “best system of emission reduction” for GHG emissions from existing coal-fired EGUs as on-site, heat-rate efficiency improvements. The proposed rule also provides states with a list of candidate technologies that can be used to establish standards of performance and incorporate these performance standards into state plans. In order for the states to be able to effectively implement the proposed emission guidelines contained in the ACE Rule, the EPA is proposing new regulations under 111(d) of the Clean Air Act to help clarify this process. In addition, the EPA is proposing revisions to the NSR program that will reduce the likelihood of triggering NSR for proposed heat-rate efficiency improvement projects at existing coal-fired EGUs. The EPA accepted comments on these three proposed regulatory changes until October 31, 2018. Due to the future uncertainty of the CPP and ACE rules, the Evergy Companies cannot determine the impact on their operations or consolidated financial results, but the cost to comply with the CPP, should it be upheld and implemented in its current or a substantially similar form, or ACE in its current or a substantially similar form, could be material. Water The Evergy Companies discharge some of the water used in generation and other operations. This water may contain substances deemed to be pollutants. Revised rules governing such discharges from coal-fired power plants were issued in November 2015. The final rule establishes effluent limitations guidelines (ELG) and standards for wastewater discharges, including limits on the amount of toxic metals and other pollutants that can be discharged. Implementation timelines for these requirements vary from 2018 to 2023. In April 2017, the EPA announced it is reconsidering the ELG rule and court challenges have been placed in abeyance pending the EPA's review. In September 2017, the EPA finalized a rule to postpone the compliance dates for the new, more stringent, effluent limitations and pretreatment standards for bottom ash transport water and flue gas desulfurization wastewater. These compliance dates have been postponed for two years while the EPA completes its administrative reconsideration of the ELG rule. The Evergy Companies are evaluating the final rule and related developments and cannot predict the resulting impact on their operations or consolidated financial results, but believe costs to comply could be material if the rule is implemented in its current or substantially similar form. In October 2014, the EPA's final standards for cooling intake structures at power plants to protect aquatic life took effect. The standards, based on Section 316(b) of the federal Clean Water Act (CWA), require subject facilities to choose among seven best available technology options to reduce fish impingement. In addition, some facilities must conduct studies to assist permitting authorities to determine whether and what site-specific controls, if any, would be required to reduce entrainment of aquatic organisms. The Evergy Companies' current analysis indicates this rule will not have a significant impact on their coal plants that employ cooling towers or cooling lakes that can be classified as closed cycle cooling and do not expect the impact from this rule to be material. Plants without closed cycle cooling are under evaluation for compliance with these standards and may require additional controls that could be material. KCP&L holds a permit from MDNR covering water discharge from its Hawthorn Station. The permit authorizes KCP&L to, among other things, withdraw water from the Missouri River for cooling purposes and return the heated water to the Missouri River. KCP&L has applied for a renewal of this permit and the EPA has submitted an interim objection letter regarding the allowable amount of heat that can be contained in the returned water. Until this matter is resolved, KCP&L continues to operate under its current permit. Evergy and KCP&L cannot predict the outcome of this matter; however, while less significant outcomes are possible, this matter may require a reduction in generation, installation of cooling towers or other technology to cool the water, or both, any of which could have a material impact on Evergy's and KCP&L's operations and consolidated financial results. In June 2015, the EPA along with the U.S. Army Corps of Engineers issued a final rule, effective August 2015, defining the Waters of the United States (WOTUS) for purposes of the CWA. This rulemaking has the potential to impact all programs under the CWA. Expansion of regulated waterways is possible under the rule depending on regulating authority interpretation, which could impact several permitting programs. Various states and others have filed lawsuits challenging the WOTUS rule. In February 2018, the EPA and the U.S. Army Corps of Engineers finalized a rule adding an applicability date to the 2015 rule, which makes the implementation date of the rule February 2020. In July 2017, the EPA and the U.S. Army Corps of Engineers published in the Federal Register a proposed rule that would, if implemented, reinstate the definition of WOTUS that existed prior to the June 2015 expansion of the definition. Final action on the proposed rule is expected in 2018 as it is currently at the Office of Management and Budget for inter-agency review. The Evergy Companies are currently evaluating the WOTUS rule and related developments but do not believe the rule, if upheld and implemented in its current or substantially similar form, will have a material impact on the Evergy Companies' operations or consolidated financial results. Regulation of Coal Combustion Residuals In the course of operating their coal generation plants, the Evergy Companies produce CCRs, including fly ash, gypsum and bottom ash. Some of this ash production is recycled, principally by selling to the aggregate industry. The EPA published a rule to regulate CCRs in April 2015, which will require additional CCR handling, processing and storage equipment and closure of certain ash disposal units. The Water Infrastructure Improvements for the Nation (WIIN) Act allows states to achieve delegated authority for CCR rules from the EPA. This has the potential to impact compliance options. In July 2018, the KDHE submitted a CCR permit program application to the EPA under authority of the WIIN Act. Final action on the application by the EPA is expected to occur within one year from the application date. MDNR is working on a rule revision which will allow the state to apply for authority over the federal CCR regulation. The application is expected to be submitted to the EPA in early 2019. Similar to the process in Kansas, this would allow Missouri state regulators to gain control of the CCR program. It will take up to one year from submittal of the Missouri application for EPA to take final action and grant authority to the state. On July 30, 2018, the EPA published in the Federal Register a final rule called the Phase I CCR Remand Rule in order to modify portions of the 2015 rulemaking. The Phase I rule provides a timeline extension for unlined impoundments and landfills that must close due to groundwater impacts or location restrictions. The rule also sets risk-based limits for certain groundwater constituents where a maximum contaminant level did not previously exist. These rule modifications add flexibility when assessing compliance. On August 21, 2018, the D.C. Circuit court issued a ruling in the CCR rule litigation between the Utility Solid Waste Activities Group, the EPA and environmental organizations. Portions of the rule were vacated and were remanded back to EPA for potential modification. Potential revisions to remanded sections could force all unlined surface impoundments to close regardless of groundwater conditions. Any changes to the rule based on this court decision will require additional rulemaking from the EPA. The Evergy Companies have recorded AROs for their current estimates for the closure of ash disposal ponds but the revision of these AROs may be required in the future due to changes in existing CCR regulations, changes in interpretation of existing CCR regulations, the results of groundwater monitoring of CCR units, or changes in the timing or cost to close ash disposal ponds. If revisions to these AROs are necessary, the impact on the Evergy Companies' operations or consolidated financial results could be material. Storage of Spent Nuclear Fuel Under the Nuclear Waste Policy Act of 1982, the Department of Energy (DOE) is responsible for the permanent disposal of spent nuclear fuel. In 2010, the DOE filed a motion with the Nuclear Regulatory Commission (NRC) to withdraw its then pending application to construct a national repository for the disposal of spent nuclear fuel and high-level radioactive waste at Yucca Mountain, Nevada. An NRC board denied the DOE's motion to withdraw its application and the DOE appealed that decision to the full NRC. In 2011, the NRC issued an evenly split decision on the appeal and also ordered the licensing board to close out its work on the DOE's application by the end of 2011 due to a lack of funding. These agency actions prompted the states of Washington and South Carolina, and a county in South Carolina, to file a lawsuit in a federal Court of Appeals asking the court to compel the NRC to resume its license review and to issue a decision on the license application. In August 2013, the court ordered the NRC to resume its review of the DOE's application. The NRC has not yet issued its decision. Wolf Creek has elected to build a dry cask storage facility to expand its existing on-site spent nuclear fuel storage, which is expected to provide additional capacity prior to 2025. Wolf Creek has finalized a settlement agreement through 2019 with the DOE for reimbursement of costs to construct this facility that would not have otherwise been incurred had the DOE begun accepting spent nuclear fuel. The Evergy Companies expect the majority of the remaining cost to construct the dry cask storage facility that would not have otherwise been incurred will be reimbursed by the DOE. The Evergy Companies cannot predict when, or if, an off-site storage site or alternative disposal site will be available to receive Wolf Creek's spent nuclear fuel and will continue to monitor this activity.

Guarantees

9 Months Ended

Sep. 30, 2018

Guarantees [Abstract]

Guarantees

13. GUARANTEES

In the ordinary course of business, Evergy and certain of its subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries. Such agreements include, for example, guarantees and letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiary's intended business purposes. The majority of these agreements guarantee the company's own future performance, so a liability for the fair value of the obligation is not recorded. In connection with the merger transaction, Evergy assumed the guarantees previously provided to GMO by Great Plains Energy.

At September 30, 2018, Evergy has provided $111.3 million of credit support for GMO as follows:


•	Evergy direct guarantees to GMO counterparties totaling $17.0 million, which expire in 2020, and


•	Evergy's guarantee of GMO long-term debt totaling $94.3 million, which includes debt with maturity dates ranging from 2019 to 2023.

Evergy has also guaranteed GMO's commercial paper program. At September 30, 2018, GMO had $140.4 million of commercial paper outstanding.

Related Party Transactions and Relationships

9 Months Ended

Sep. 30, 2018

14. RELATED PARTY TRANSACTIONS AND RELATIONSHIPS

In the normal course of business, Westar Energy, KCP&L and GMO engage in related party transactions with one another. A summary of these transactions and the amounts associated with them is provided below. All related party transaction amounts between Westar Energy and either KCP&L or GMO only reflect activity between June 4, 2018, the date of the merger, and September 30, 2018.

Jointly-Owned Plants and Shared Services

KCP&L employees manage GMO's business and operate its facilities at cost, including GMO's 18% ownership interest in KCP&L's Iatan Nos. 1 and 2. The operating expenses and capital costs billed from KCP&L to GMO were $43.4 million and $139.6 million, respectively, for the three months ended and year to date September 30, 2018. These costs totaled $49.2 million and $145.0 million, respectively, for the three months ended and year to date September 30, 2017.

Westar Energy employees manage Jeffrey Energy Center and operate its facilities at cost, including GMO's 8% ownership interest in Jeffrey Energy Center. The operating expenses and capital costs billed from Westar Energy to GMO for Jeffrey Energy Center and other various business activities were $0.8 million and $4.5 million, respectively, for the three months ended and year to date September 30, 2018.

KCP&L employees manage La Cygne Station and operate its facilities at cost, including Westar Energy's 50% ownership interest in La Cygne Station. KCP&L and Westar Energy employees also provide one another with shared service support, including costs related to human resources, information technology, accounting and legal services. The operating expenses and capital costs billed from KCP&L to Westar Energy were $35.5 million and $50.8 million, respectively, for the three months ended and year to date September 30, 2018. The operating and capital costs billed from Westar Energy to KCP&L were $4.8 million and $10.8 million, respectively, for the three months ended and year to date September 30, 2018.

Money Pool

KCP&L and GMO are also authorized to participate in the Evergy money pool, an internal financing arrangement in which funds may be lent on a short-term basis to KCP&L and GMO from Evergy and between KCP&L and GMO. At September 30, 2018 and December 31, 2017, KCP&L had no outstanding receivables or payables under the money pool.

The following table summarizes Westar Energy's and KCP&L's related party net receivables and payables.



	September 30			December 31
	2018			2017
Westar Energy	(millions)
Net receivable from GMO	$	0.7		$	—
Net payable to KCP&L	(59.3		)	—
Net payable to Evergy	(14.6		)	—

KCP&L
Net receivable from GMO	$	63.3		$	65.8
Net receivable from Westar Energy	59.3			—
Net receivable from Evergy	16.4			—
Net receivable from Great Plains Energy	—			18.9

Tax Allocation Agreement

Evergy files a consolidated federal income tax return as well as unitary and combined income tax returns in several state jurisdictions with Kansas and Missouri being the most significant. Income taxes for consolidated or combined subsidiaries are allocated to the subsidiaries based on separate company computations of income or loss. As of September 30, 2018, Westar Energy and KCP&L had income taxes payable to Evergy of $4.4 million and $21.4 million, respectively.

Shareholders' Equity	9 Months Ended
Shareholders' Equity	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Shareholders' Equity	15. SHAREHOLDERS' EQUITY Evergy's authorized capital stock consists of 600 million shares of common stock, without par value, and 12 million shares of Preference Stock, without par value. Evergy Registration Statements In November 2018, Evergy filed an automatic shelf registration statement providing for the sale of unlimited amounts of securities with the SEC, which expires in November 2021. In September 2018, Evergy registered shares of its common stock with the SEC for its Dividend Reinvestment and Direct Stock Purchase Plan. Shares issued under the plan may be either newly issued shares or shares purchased on the open market. In June 2018, Evergy registered shares of its common stock with the SEC for the Great Plains Energy 401(k) Savings Plan and Westar Energy, Inc. Employees' 401(k) Savings Plan, among other compensation plans, that Evergy assumed in connection with the merger transaction. Shares issued under the plans may be either newly issued shares or shares purchased on the open market. Common Stock Repurchase Plan In July 2018, the Evergy Board authorized the repurchase of up to 60 million shares of Evergy's common stock. Although this repurchase authorization has no expiration date, Evergy expects to repurchase the 60 million shares by mid-2020. Evergy plans to utilize various methods to effectuate the share repurchase program, including but not limited to, a series of transactions that may include accelerated share repurchases, open market transactions or other means, subject to market conditions and applicable legal requirements. The repurchase program may be suspended, discontinued or resumed at any time. Year to date September 30, 2018, Evergy had total repurchases of common stock of approximately $486 million and had repurchased 6.9 million shares under the repurchase program, which included shares repurchased under accelerated share repurchase (ASR) agreements which had not reached final settlement as of September 30, 2018, and are discussed further below. Evergy retires repurchased common stock shares in the period the shares are repurchased. In August 2018, Evergy entered into two ASR agreements with financial institutions to purchase $450.0 million of Evergy common stock. In August 2018, the financial institutions delivered to Evergy 6.3 million shares of common stock, representing a partial settlement of the contracts, based on then-current market prices and Evergy paid a total of $450.0 million. The upfront payment was recorded as a reduction to Evergy, Inc. shareholders' equity on Evergy's consolidated balance sheets and as a repurchase of common stock on Evergy's consolidated statements of cash flows. The final number of shares of Evergy common stock that Evergy may receive or be required to remit upon final settlement of the ASR agreements will be based on the average daily volume weighted-average price of Evergy common stock during the term of the ASR agreements, less a negotiated discount. Final settlement of each ASR agreement will occur by the end of November 2018 but may occur earlier at the option of the financial institutions. In October 2018, one of the ASR agreements was settled early at the option of the financial institution, which resulted in the delivery to Evergy of 848,226 additional shares of Evergy common stock at no additional cost. Evergy expects that the final settlement of the remaining ASR agreement will also result in the delivery of additional shares of common stock to Evergy at no additional cost. Evergy reflects the ASRs as a repurchase of common stock in the period the shares are delivered for purposes of calculating earnings per share and as forward contracts indexed to its own common stock. The ASRs meet all of the applicable criteria for equity classification and therefore are not accounted for as derivative instruments. Dividend Restrictions Evergy depends on its subsidiaries to pay dividends on its common stock. The Evergy Companies have certain restrictions stemming from statutory requirements, corporate organizational documents, covenants and other conditions that could affect dividend levels or the ability to pay dividends. The KCC order authorizing the merger transaction requires Evergy to maintain consolidated common equity of at least 35% of total consolidated capitalization. Further, Evergy's master credit facility requires it to maintain a consolidated indebtedness to consolidated capitalization ratio of not more than 0.65 to 1.00 at all times. Under the Federal Power Act, Westar Energy, KCP&L and GMO generally can pay dividends only out of retained earnings. Certain conditions in the MPSC and KCC orders authorizing the merger transaction also require Westar Energy and KCP&L to maintain consolidated common equity of at least 40% of total capitalization. Other conditions in the MPSC and KCC merger orders require Westar Energy, KCP&L and GMO to maintain credit ratings of at least investment grade. If Westar Energy's, KCP&L's or GMO's credit ratings are downgraded below the investment grade level as a result of their affiliation with Evergy or any of Evergy's affiliates, the impacted utility shall not pay a common dividend without KCC or MPSC approval or until the impacted utility's investment grade credit rating has been restored. The master credit facility of Evergy, Westar Energy, KCP&L and GMO and the note purchase agreement for GMO's Series A, B and C Senior Notes contain covenants requiring the respective company to maintain a consolidated indebtedness to consolidated total capitalization ratio of not more than 0.65 to 1.00 at all times. As of September 30, 2018, all of Evergy's and Westar Energy's retained earnings and net income were free of restrictions and KCP&L had a retained earnings restriction of $227.4 million. Evergy's subsidiaries had restricted net assets of approximately $5.2 billion as of September 30, 2018. These restrictions are not expected to affect the Evergy Companies' ability to pay dividends at the current level for the foreseeable future.

Variable Interest Entities

9 Months Ended

Sep. 30, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Variable Interest Entities

16. VARIABLE INTEREST ENTITIES

In determining the primary beneficiary of a VIE, the Evergy Companies assess the entity's purpose and design, including the nature of the entity's activities and the risks that the entity was designed to create and pass through to its variable interest holders. A reporting enterprise is deemed to be the primary beneficiary of a VIE if it has (a) the power to direct the activities of the VIE that most significantly impact the VIE's economic performance and (b) the obligation to absorb losses or right to receive benefits from the VIE that could potentially be significant to the VIE. The primary beneficiary of a VIE is required to consolidate the VIE. The trust holding an 8% interest in Jeffrey Energy Center was a VIE until the expiration of a purchase option in July 2017. The trust holding KGE's 50% interest in La Cygne Unit 2 is a VIE and KGE remains the primary beneficiary of the trust.

All involvement with entities by the Evergy Companies is assessed to determine whether such entities are VIEs and, if so, whether or not the Evergy Companies are the primary beneficiaries of the entities. The Evergy Companies also continuously assess whether they are the primary beneficiary of the VIE with which they are involved. Prospective changes in facts and circumstances may cause identification of the primary beneficiary to be reconsidered.

8% Interest in Jeffrey Energy Center

Under an agreement that expires in January 2019, Westar Energy leases an 8% interest in Jeffrey Energy Center from a trust. The trust was financed with an equity contribution from an owner participant and debt issued by the trust. The trust was created specifically to purchase the 8% interest in Jeffrey Energy Center and lease it to a third party, and does not hold any other assets. Westar Energy met the requirements to be considered the primary beneficiary of the trust until July 2017, when a contractual option to purchase the 8% interest in the plant covered by the lease expired. Accordingly, Westar Energy deconsolidated the trust in the third quarter of 2017.

50% Interest in La Cygne Unit 2

Under an agreement that expires in September 2029, KGE entered into a sale-leaseback transaction with a trust under which the trust purchased KGE's 50% interest in La Cygne Unit 2 and subsequently leased it back to KGE. The trust was financed with an equity contribution from an owner participant and debt issued by the trust. The trust was created specifically to purchase the 50% interest in La Cygne Unit 2 and lease it back to KGE, and does not hold any other assets. KGE meets the requirements to be considered the primary beneficiary of the trust. In determining the primary beneficiary of the trust, KGE concluded that the activities of the trust that most significantly impact its economic performance and that KGE has the power to direct include (1) the operation and maintenance of the 50% interest in La Cygne Unit 2 and (2) KGE's ability to exercise a purchase option at the end of the agreement at the lesser of fair value or a fixed amount. KGE has the potential to receive benefits from the trust that could potentially be significant if the fair value of the 50% interest in La Cygne Unit 2 at the end of the agreement is greater than the fixed amount.

The following table summarizes the assets and liabilities related to the VIE described above that are recorded on Evergy's and Westar Energy's consolidated balance sheets.



	September 30		December 31
	2018		2017
Assets:	(millions)
Property, plant and equipment of variable interest entities, net	$	170.9	$	176.3
Liabilities:
Current maturities of long-term debt of variable interest entities	$	30.3	$	28.5
Accrued interest^(a)	—		0.7
Long-term debt of variable interest entities, net	51.1		81.4


^(a)	Included in accrued interest on Evergy's and Westar Energy's consolidated balance sheets.

All of the liabilities noted in the table above relate to the purchase of the property, plant and equipment of the VIE. The assets of the VIE can be used only to settle obligations of the VIE and the VIE's debt holders have no recourse to the general credit of Evergy and Westar Energy. Evergy and Westar Energy have not provided financial or other support to the VIE and are not required to provide such support. Evergy and Westar Energy did not record any gain or loss upon the initial consolidation of the VIE.

Taxes

9 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Income Tax Disclosure [Text Block]

17. TAXES

Components of income tax expense are detailed in the following tables.



Evergy
	Three Months Ended September 30						Year to Date September 30
	2018			2017			2018			2017
Current income taxes	(millions)
Federal	$	(30.3	)	$	(16.7	)	$	(21.5	)	$	(14.5	)
State	1.5			—			1.9			0.4
Total	(28.8		)	(16.7		)	(19.6		)	(14.1		)
Deferred income taxes
Federal	70.6			58.8			86.0			101.7
State	23.3			14.3			(35.7		)	27.0
Total	93.9			73.1			50.3			128.7
Investment tax credit amortization	(1.0		)	(0.6		)	(2.4		)	(2.0		)
Income tax expense	$	64.1		$	55.8		$	28.3		$	112.6



Westar Energy
	Three Months Ended September 30						Year to Date September 30
	2018			2017			2018			2017
Current income taxes	(millions)
Federal	$	8.0		$	(16.7	)	$	18.9		$	(14.5	)
State	(9.2		)	—			(6.7		)	0.4
Total	(1.2		)	(16.7		)	12.2			(14.1		)
Deferred income taxes
Federal	12.3			58.8			15.4			101.7
State	12.0			14.3			(47.6		)	27.0
Total	24.3			73.1			(32.2		)	128.7
Investment tax credit amortization	(0.7		)	(0.6		)	(2.0		)	(2.0		)
Income tax expense (benefit)	$	22.4		$	55.8		$	(22.0	)	$	112.6



KCP&L
	Three Months Ended September 30						Year to Date September 30
	2018			2017			2018			2017
Current income taxes	(millions)
Federal	$	20.7		$	41.8		$	43.5		$	56.2
State	6.8			7.6			11.6			10.2
Total	27.5			49.4			55.1			66.4
Deferred income taxes
Federal	(1.9		)	10.3			(23.4		)	27.2
State	2.7			2.8			49.4			6.2
Total	0.8			13.1			26.0			33.4
Investment tax credit amortization	(0.3		)	(0.3		)	(0.8		)	(0.8		)
Income tax expense	$	28.0		$	62.2		$	80.3		$	99.0

Effective Income Tax Rates

Effective income tax rates reflected in the financial statements and the reasons for their differences from the statutory federal rates are detailed in the following tables.



Evergy
	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Federal statutory income tax rate	21.0	%	35.0	%	21.0	%	35.0	%
Effect of:
COLI policies	(2.4	)	(4.6	)	(2.4	)	(4.5	)
State income taxes	4.6		4.3		4.7		4.3
Flow through depreciation for plant-related differences	(1.5	)	2.3		(1.6	)	2.8
Federal tax credits	(7.5	)	(7.1	)	(7.5	)	(7.0	)
Non-controlling interest	(0.4	)	(0.5	)	(0.4	)	(0.8	)
AFUDC equity	(0.1	)	(0.2	)	(0.1	)	(0.2	)
Amortization of federal investment tax credits	(0.6	)	(0.6	)	(0.6	)	(0.6	)
State tax rate change	0.1		—		(9.5	)	—
Valuation allowance	—		—		0.4		—
Stock compensation	—		—		(0.5	)	(1.0	)
Officer compensation limitation	1.2		—		1.2		—
Other	0.8		(2.8	)	0.4		(0.7	)
Effective income tax rate	15.2	%	25.8	%	5.1	%	27.3	%

The decrease in Evergy's state tax rate change for year to date September 30, 2018, compared to the same period in 2017, is primarily due to the revaluation of Westar Energy's state deferred income tax assets and liabilities based on the Evergy composite tax rate as a result of the merger.



Westar Energy
	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Federal statutory income tax rate	21.0	%	35.0	%	21.0	%	35.0	%
Effect of:
COLI policies	(4.0	)	(4.6	)	(4.0	)	(4.5	)
State income taxes	1.1		4.3		3.3		4.3
Flow through depreciation for plant-related differences	1.5		2.3		0.3		2.8
Federal tax credits	(11.8	)	(7.1	)	(11.7	)	(7.0	)
Non-controlling interest	(0.6	)	(0.5	)	(0.7	)	(0.8	)
AFUDC equity	(0.1	)	(0.2	)	(0.1	)	(0.2	)
Amortization of federal investment tax credits	(0.8	)	(0.6	)	(0.8	)	(0.6	)
Changes in uncertain tax positions, net	0.1		—		0.1		—
State tax rate change	—		—		(17.7	)	—
Valuation allowance	—		—		0.6		—
Stock compensation	—		—		(0.9	)	(1.0	)
Officer compensation limitation	1.9		—		1.9		—
Other	2.9		(2.8	)	1.3		(0.7	)
Effective income tax rate	11.2	%	25.8	%	(7.4	)%	27.3	%

The decrease in Westar Energy's state tax rate change for year to date September 30, 2018, compared to the same period in 2017, is primarily due to the revaluation of Westar Energy's state deferred income tax assets and liabilities based on the Evergy composite tax rate as a result of the merger.



KCP&L
	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Federal statutory income tax rate	21.0	%	35.0	%	21.0	%	35.0	%
Effect of:
COLI policies	(0.2	)	(0.3	)	(0.2	)	(0.3	)
State income taxes	5.0		3.9		5.1		3.9
Flow through depreciation for plant-related differences	(4.9	)	0.1		(4.9	)	0.2
Federal tax credits	(1.9	)	(3.1	)	(1.8	)	(2.6	)
AFUDC equity	—		(0.7	)	(0.1	)	(0.7	)
Amortization of federal investment tax credits	(0.4	)	(0.4	)	(0.4	)	(0.4	)
State tax rate change	—		—		14.5		—
Valuation allowance	—		0.6		—		0.4
Stock compensation	—		0.1		—		0.2
Officer compensation limitation	0.7		—		0.5		—
Other	(0.4	)	0.1		(1.0	)	0.1
Effective income tax rate	18.9	%	35.3	%	32.7	%	35.8	%

The increase in KCP&L's state tax rate change for year to date September 30, 2018, compared to the same period in 2017, is primarily due to the revaluation of KCP&L's state deferred income tax assets and liabilities based on the Evergy composite tax rate as a result of the merger, partially offset by a revaluation of KCP&L's state deferred income tax assets and liabilities as a result of the enactment of Missouri state income tax reform in June 2018.

Federal Tax Reform

In December 2017, the U.S. Congress passed and President Donald Trump signed Public Law No. 115-97, commonly referred to as the Tax Cuts and Jobs Act. The Tax Cuts and Jobs Act represents the first major reform in U.S. income tax law since 1986. Most notably, the Tax Cuts and Jobs Act reduces the current top corporate income tax rate from 35% to 21% beginning in 2018, repeals the corporate Alternative Minimum Tax (AMT), makes existing AMT tax credit carryforwards refundable, and changes the deductibility and taxability of certain items, among other things. Prior to the change in tax rates that has been reflected in their 2018 rate cases,Westar Energy, KCP&L and GMO recovered the cost of income taxes in rates from their customers based on the 35% federal corporate income tax rate.

In January 2018, the KCC issued an order requiring certain regulated public utilities, including Westar Energy and KCP&L, to begin recording a regulatory liability for the difference between the new corporate tax rate and amounts currently collected in rates. In May 2018 and June 2018, Westar Energy and KCP&L entered into settlement agreements with KCC staff and other intervenors in which they further agreed to begin deferring any impacts of the Tax Cuts and Jobs Act on their excess accumulated deferred income taxes to a regulatory liability. The KCC approved these settlement agreements in June 2018. KCP&L and GMO had also recorded regulatory liabilities in 2018 due to the probability that they would also be required to make similar refunds to their Missouri customers. The final regulatory treatment of these regulatory liabilities was determined in each of Westar Energy's, KCP&L's and GMO's rate cases with the KCC and MPSC. See Note 5 for more information.

As of September 30, 2018, Evergy, Westar Energy and KCP&L had recorded regulatory liabilities for refunds to customers related to the impacts of the Tax Cuts and Jobs Act of $155.1 million, $66.3 million and $64.6 million, respectively.

Missouri Tax Reform

On June 1, 2018, the Missouri governor signed Senate Bill (S.B.) 884 into law. Most notably, S.B. 884 reduces the corporate income tax rate from 6.25% to 4.0% beginning in 2020, provides for the mandatory use of the single sales factor formula and eliminates intercompany transactions between corporations that file a consolidated Missouri income tax return.

As a result of the change in the Missouri corporate income tax rate, KCP&L revalued and restated its deferred income tax assets and liabilities as of June 1, 2018. KCP&L decreased its net deferred income tax liabilities by $46.6 million, primarily consisting of a $28.8 million adjustment for the revaluation and restatement of deferred income tax assets and liabilities included in Missouri jurisdictional rate base and a $9.9 million tax gross-up adjustment for ratemaking purposes. The decrease to KCP&L's net deferred income tax liabilities included in Missouri jurisdictional rate base were offset by a corresponding increase in regulatory liabilities. The net regulatory liabilities will be amortized to customers over a period to be determined in a future rate case.

KCP&L recognized $15.5 million of income tax benefit primarily related to the difference between KCP&L's revaluation of its deferred income tax assets and liabilities for financial reporting purposes and the amount of the revaluation pertaining to KCP&L's Missouri jurisdictional rate base.

Organization and Basis of Presentation (Policies)

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Principles of Consolidation

Fuel Inventory and Supplies

The Evergy Companies record fuel inventory and supplies at average cost.

Earnings Per Share

New Accounting Standards

Intangibles - Internal-Use Software

Compensation - Retirement Benefits



	Three Months Ended									Year to Date
	September 30, 2017									September 30, 2017
	As Previously Reported^(b)			Effect of Change			As Reported			As Previously Reported^(b)			Effect of Change			As Reported
Evergy	(millions)
Operating and maintenance expense	$	145.5		$	(4.9	)	$	140.6		$	430.6		$	(15.0	)	$	415.6
Total operating expenses	534.3			(4.9		)	529.4			1,434.7			(15.0		)	1,419.7
Income from operations	260.0			4.9			264.9			541.5			15.0			556.5
Other expense	(6.6		)	(4.9		)	(11.5		)	(14.6		)	(15.0		)	(29.6		)
Total other income (expense), net	(1.7		)	(4.9		)	(6.6		)	(5.4		)	(15.0		)	(20.4		)
Westar Energy
Operating and maintenance expense	$	145.5		$	(4.9	)	$	140.6		$	430.6		$	(15.0	)	$	415.6
Total operating expenses	534.3			(4.9		)	529.4			1,434.7			(15.0		)	1,419.7
Income from operations	260.0			4.9			264.9			541.5			15.0			556.5
Other expense	(6.6		)	(4.9		)	(11.5		)	(14.6		)	(15.0		)	(29.6		)
Total other income (expense), net	(1.7		)	(4.9		)	(6.6		)	(5.4		)	(15.0		)	(20.4		)
KCP&L^(a)
Operating and maintenance expense	$	124.2		$	(9.9	)	$	114.3		$	385.0		$	(34.3	)	$	350.7
Total operating expenses	385.8			(9.9		)	375.9			1,092.4			(34.3		)	1,058.1
Income from operations	209.9			9.9			219.8			381.9			34.3			416.2
Other expense	(2.0		)	(9.9		)	(11.9		)	(6.4		)	(34.3		)	(40.7		)
Total other income (expense), net	0.7			(9.9		)	(9.2		)	0.5			(34.3		)	(33.8		)

^(a)KCP&L amounts are not included in consolidated Evergy for the three months ended and year to date September 30, 2017.

Statement of Cash Flows

Leases

Financial Instruments

Revenue Recognition

Organization and Basis of Presentation (Tables)

9 Months Ended

Sep. 30, 2018

Accounting Policies [Abstract]

Summary of Reclassifications

The table below summarizes KCP&L's reclassifications related to operating and investing activities for its consolidated statement of cash flows for year to date September 30, 2017.



	Year to Date
	September 30, 2017
	As Filed			Updated
CASH FLOWS FROM (USED IN) OPERATING ACTIVITIES:	(in millions)
Adjustments to reconcile income to net cash from operating activities:
Amortization of other	$	23.4		$	—
Amortization of deferred refueling outage	—			13.7
Deferred income taxes, net	33.4			—
Investment tax credit amortization	(0.8		)	—
Net deferred income taxes and credits	—			32.6
Payments for asset retirement obligations	—			(14.9		)
Other^(a)	(16.0		)	6.3
Changes in working capital items:
Fuel inventory and supplies	—			3.6
Fuel inventories^(a)	10.8			—
Materials and supplies^(a)	(7.2		)	—
Prepaid expenses and other current assets	—			8.9
Accrued interest^(a)	8.1			—
Other current liabilities	—			9.9
Changes in other assets	—			52.6
Changes in other liabilities	—			7.3
Deferred refueling outage costs^(a)	12.1			—
Pension and post-retirement benefit obligations^(a)	48.6			—
Fuel recovery mechanisms^(a)	7.6			—
Total reclassifications	$	120.0		$	120.0
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Additions to property, plant and equipment	$	—		$	(317.1	)
Utility capital expenditures	(295.1		)	—
Allowance for borrowed funds used during construction	(4.2		)	—
Other investing activities	(17.0		)	0.8
Total reclassifications	$	(316.3	)	$	(316.3	)

^(a)Previously reported within Note 3 to the consolidated financial statements of the Great Plains Energy and KCP&L combined Third Quarter 2017 Quarterly Report on Form 10-Q.

Schedule of Fuel Inventory and Supplies

The balances for fuel inventory and supplies are stated separately in the table below.



	September 30			December 31
		2018			2017
Evergy		(millions)
Fuel inventory		$	163.1		$	94.1
Supplies		357.8			199.5
Fuel inventory and supplies		$	520.9		$	293.6
Westar Energy
Fuel inventory		$	84.9		$	94.1
Supplies		183.8			199.5
Fuel inventory and supplies		$	268.7		$	293.6
KCP&L^(a)
Fuel inventory		$	54.6		$	71.0
Supplies		129.2			126.0
Fuel inventory and supplies		$	183.8		$	197.0

^(a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Summary of Property, Plant and Equipment

The following tables summarize the property, plant and equipment of Evergy, Westar Energy and KCP&L.



September 30, 2018	Evergy			Westar Energy			KCP&L
	(millions)
Electric plant in service	$	27,290.0		$	13,236.1		$	10,594.2
Electric plant acquisition adjustment	740.6			740.6			—
Accumulated depreciation	(10,168.2		)	(4,838.9		)	(4,172.3		)
Plant in service	17,862.4			9,137.8			6,421.9
Construction work in progress	723.5			443.6			183.4
Nuclear fuel, net	109.1			54.1			55.0
Plant to be retired, net^(b)	141.0			2.0			—
Property, plant and equipment, net	$	18,836.0		$	9,637.5		$	6,660.3

December 31, 2017	Evergy			Westar Energy			KCP&L^(a)
	(millions)
Electric plant in service	$	12,954.3		$	12,954.3		$	10,213.2
Electric plant acquisition adjustment	739.0			739.0			—
Accumulated depreciation	(4,651.7		)	(4,651.7		)	(4,070.3		)
Plant in service	9,041.6			9,041.6			6,142.9
Construction work in progress	434.9			434.9			350.3
Nuclear fuel, net	71.4			71.4			72.4
Plant to be retired, net^(b)	5.9			5.9			—
Property, plant and equipment, net	$	9,553.8		$	9,553.8		$	6,565.6

^(a) KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Schedule of Earnings Per Share, Basic and Diluted

The following table reconciles Evergy's basic and diluted EPS.



	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Income	(millions, except per share amounts)
Net income	$	357.6	$	160.7	$	524.9	$	300.2
Less: net income attributable to noncontrolling interests	2.6		2.4		7.6		10.2
Net income attributable to Evergy, Inc.	355.0		158.3		517.3		290.0
Less: net income allocated to RSUs	0.2		0.3		0.4		0.5
Net income allocated to common stock	$	354.8	$	158.0	$	516.9	$	289.5
Common Shares Outstanding
Weighted average equivalent common shares outstanding - basic	268.6		142.5		197.9		142.5
Add: effect of dilutive securities	0.2		—		0.1		—
Weighted average equivalent common shares outstanding - diluted	268.8		142.5		198.0		142.5
Basic and Diluted EPS	$	1.32	$	1.11	$	2.61	$	2.03

Supplemental Cash Flow Information



Year to Date September 30	2018			2017
Evergy	(millions)
Cash paid for (received from):
Interest, net of amounts capitalized	$	148.7		$	109.0
Interest of VIEs	2.3			3.1
Income taxes, net of refunds	0.6			(12.6		)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(24.8		)	112.5
Deconsolidation of property, plant and equipment of VIE	—			(72.9		)
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	0.4			4.9
Deconsolidation of VIE	—			(83.1		)
Assets acquired through capital leases	0.1			4.6
Westar Energy
Cash paid for (received from):
Interest, net of amounts capitalized	$	110.5		$	109.0
Interest of VIEs	2.3			3.1
Income taxes, net of refunds	—			(12.6		)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(42.0		)	112.5
Deconsolidation of property, plant and equipment of VIE	—			(72.9		)
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	—			4.9
Deconsolidation of VIE	—			(83.1		)
Assets acquired through capital leases	0.1			4.6
KCP&L^(a)
Cash paid for (received from):
Interest, net of amounts capitalized	$	87.6		$	88.6
Income taxes, net of refunds	28.4			4.9
Non-cash investing transactions:
Property, plant and equipment additions	15.2			15.5

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Schedule of Retrospective Adjustments



	Three Months Ended									Year to Date
	September 30, 2017									September 30, 2017
	As Previously Reported^(b)			Effect of Change			As Reported			As Previously Reported^(b)			Effect of Change			As Reported
Evergy	(millions)
Operating and maintenance expense	$	145.5		$	(4.9	)	$	140.6		$	430.6		$	(15.0	)	$	415.6
Total operating expenses	534.3			(4.9		)	529.4			1,434.7			(15.0		)	1,419.7
Income from operations	260.0			4.9			264.9			541.5			15.0			556.5
Other expense	(6.6		)	(4.9		)	(11.5		)	(14.6		)	(15.0		)	(29.6		)
Total other income (expense), net	(1.7		)	(4.9		)	(6.6		)	(5.4		)	(15.0		)	(20.4		)
Westar Energy
Operating and maintenance expense	$	145.5		$	(4.9	)	$	140.6		$	430.6		$	(15.0	)	$	415.6
Total operating expenses	534.3			(4.9		)	529.4			1,434.7			(15.0		)	1,419.7
Income from operations	260.0			4.9			264.9			541.5			15.0			556.5
Other expense	(6.6		)	(4.9		)	(11.5		)	(14.6		)	(15.0		)	(29.6		)
Total other income (expense), net	(1.7		)	(4.9		)	(6.6		)	(5.4		)	(15.0		)	(20.4		)
KCP&L^(a)
Operating and maintenance expense	$	124.2		$	(9.9	)	$	114.3		$	385.0		$	(34.3	)	$	350.7
Total operating expenses	385.8			(9.9		)	375.9			1,092.4			(34.3		)	1,058.1
Income from operations	209.9			9.9			219.8			381.9			34.3			416.2
Other expense	(2.0		)	(9.9		)	(11.9		)	(6.4		)	(34.3		)	(40.7		)
Total other income (expense), net	0.7			(9.9		)	(9.2		)	0.5			(34.3		)	(33.8		)

^(a)KCP&L amounts are not included in consolidated Evergy for the three months ended and year to date September 30, 2017.

Merger of Great Plains Energy and Westar Energy (Tables)

9 Months Ended

Sep. 30, 2018

Business Combinations [Abstract]

Schedule of Pre-tax Costs and Deferrals and Purchase Price Allocation



Description	Income Statement Line Item	Expected Payment Period	Evergy			Westar Energy			KCP&L
			(millions)
One-time bill credits	Operating revenues	2018 - 2019	$	(59.7	)	$	(23.1	)	$	(22.4	)
Annual bill credits	Operating revenues	2019 - 2022	(7.6		)	(5.8		)	(1.9		)
Total impact to operating revenues			$	(67.3	)	$	(28.9	)	$	(24.3	)

Charitable contributions and community support	Operating and maintenance	2018 - 2027	$	24.7		$	—		$	—
Voluntary severance and accelerated equity compensation	Operating and maintenance	2018 - 2019	40.7			40.7			—
Other transaction and transition costs	Operating and maintenance	2018	47.0			20.4			1.7
Reallocation and deferral of merger transition costs	Operating and maintenance	n/a	(47.8		)	(13.3		)	(23.9		)
Total impact to operating and maintenance expense			$	64.6		$	47.8		$	(22.2	)
Total			$	(131.9	)	$	(76.7	)	$	(2.1	)

The total consideration transferred in the merger is based on the closing stock price of Westar Energy on June 4, 2018 and is calculated as follows.



	(millions, except share amounts)
Great Plains Energy common stock shares outstanding as of June 4, 2018	215,800,074
Great Plains Energy restricted stock awards outstanding as of June 4, 2018	(204,825		)
Great Plains Energy shares to be converted to Evergy shares	215,595,249
Exchange ratio	0.5981
Evergy common stock shares issued to Great Plains Energy shareholders	128,947,518
Closing price of Westar Energy common stock as of June 4, 2018	$	54.00
Fair value of Evergy shares issued to Great Plains Energy shareholders	$	6,963.2
Fair value of Great Plains Energy's equity compensation awards	12.5
Total purchase price	$	6,975.7

Schedule of Assets Acquired and Liabilities Assumed

The preliminary purchase price allocation to Great Plains Energy's assets and liabilities as of June 4, 2018 is detailed in the following table.



	(millions)
Current assets	$	2,151.7
Property, plant and equipment, net	9,179.7
Goodwill	2,333.5
Other long-term assets, excluding goodwill	1,235.9
Total assets	$	14,900.8
Current liabilities	1,673.9
Long-term liabilities, excluding long-term debt	2,892.6
Long-term debt, net	3,358.6
Total liabilities	$	7,925.1
Total purchase price	$	6,975.7

Unaudited Pro Forma Financial Information



	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
	(millions, except per share amounts)
Operating revenues	$	1,582.5	$	1,651.5	$	4,134.8	$	4,086.7
Net income attributable to Evergy, Inc.	360.2		321.8		694.5		543.3
Basic earnings per common share	$	1.34	$	1.19	$	2.56	$	2.00
Diluted earnings per common share	$	1.34	$	1.19	$	2.55	$	2.00

Revenue (Tables)

9 Months Ended

Sep. 30, 2018

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

Evergy's, Westar Energy's and KCP&L's revenues disaggregated by customer class are summarized in the following tables.



Three Months Ended September 30, 2018	Evergy		Westar Energy		KCP&L
Revenues	(millions)
Residential	$	647.1	$	270.5	$	243.5
Commercial	530.5		217.4		231.1
Industrial	173.4		111.9		39.1
Other retail	10.9		5.4		2.7
Total electric retail	$	1,361.9	$	605.2	$	516.4
Wholesale	118.5		82.4		29.9
Transmission	80.6		72.2		3.8
Industrial steam and other	6.0		1.5		0.7
Total revenue from contracts with customers	$	1,567.0	$	761.3	$	550.8
Other	15.5		3.5		8.8
Operating revenues	$	1,582.5	$	764.8	$	559.6

Year to Date September 30, 2018	Evergy		Westar Energy		KCP&L^(a)
Revenues	(millions)
Residential	$	1,169.4	$	671.9	$	585.4
Commercial	945.0		542.8		609.2
Industrial	375.5		297.2		105.4
Other retail	21.5		15.3		7.7
Total electric retail	$	2,511.4	$	1,527.2	$	1,307.7
Wholesale	302.4		263.7		38.5
Transmission	227.6		216.3		11.0
Industrial steam and other	10.0		4.6		3.0
Total revenue from contracts with customers	$	3,051.4	$	2,011.8	$	1,360.2
Other	24.7		4.1		48.7
Operating revenues	$	3,076.1	$	2,015.9	$	1,408.9

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Receivables (Tables)

9 Months Ended

Sep. 30, 2018

Receivables [Abstract]

Schedule of Receivables

The Evergy Companies' receivables are detailed in the following table.



	September 30				December 31
		2018				2017
Evergy		(millions)
Customer accounts receivable - billed		$	231.7			$	165.4
Customer accounts receivable - unbilled		191.1				76.6
Other receivables		82.4				55.4
Allowance for doubtful accounts		(8.7		)		(6.7		)
Total		$	496.5			$	290.7
Westar Energy
Customer accounts receivable - billed		$	194.0			$	165.4
Customer accounts receivable - unbilled		96.7				76.6
Other receivables		60.7				55.4
Allowance for doubtful accounts		(3.9		)		(6.7		)
Total		$	347.5			$	290.7
KCP&L ^(a)
Customer accounts receivable - billed		$	25.3			$	1.6
Customer accounts receivable - unbilled		66.6				67.6
Other receivables		14.5				39.3
Allowance for doubtful accounts		(3.5		)		(2.2		)
Total		$	102.9			$	106.3

^(a)KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Summary of Bad Debt Expense

The Evergy Companies recorded bad debt expense related to contracts with customers as summarized in the following table.



	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
	(millions)
Evergy	$	4.5	$	2.0	$	10.6	$	5.4
Westar Energy	1.1		2.0		6.2		5.4
KCP&L ^(a)	3.9		2.8		7.5		6.0

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2018

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Change in Asset Retirement Obligation

The following table summarizes the change in the Evergy Companies' AROs for the periods ending September 30, 2018 and December 31, 2017.



	Evergy						Westar Energy						KCP&L^(a)
	2018			2017			2018			2017			2018			2017
	(millions)
Beginning balance, January 1	$	405.1		$	324.0		$	405.1		$	324.0		$	266.3		$	278.0
Liabilities assumed upon merger with Great Plains Energy	412.2			—			—			—			—			—
Liabilities incurred during the year	7.4			13.5			7.4			13.5			—			—
Revision in timing and/or estimates	(138.6		)	66.8			(133.0		)	66.8			(5.7		)	0.3
Settlements	(15.9		)	(16.0		)	(10.6		)	(16.0		)	(9.9		)	(25.5		)
Accretion	22.1			16.8			14.0			16.8			12.6			13.5
Ending balance	$	692.3		$	405.1		$	282.9		$	405.1		$	263.3		$	266.3
Less: current portion	(69.6		)	(25.1		)	(25.1		)	(25.1		)	(40.6		)	(34.9		)
Total noncurrent asset retirement obligation	$	622.7		$	380.0		$	257.8		$	380.0		$	222.7		$	231.4

^(a)KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Pension Plans and Other Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2018

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

The following tables provide the components of net periodic benefit costs prior to the effects of capitalization and sharing with joint owners of power plants.



	Pension Benefits									Post-Retirement Benefits
Three Months Ended September 30, 2018	Evergy			Westar Energy			KCP&L			Evergy			Westar Energy			KCP&L
Components of net periodic benefit costs	(millions)
Service cost	$	20.2		$	8.0		$	9.1		$	0.7		$	0.4		$	0.4
Interest cost	26.3			12.7			9.4			2.5			1.2			0.8
Expected return on plan assets	(27.0		)	(13.9		)	(10.6		)	(2.5		)	(1.8		)	(0.4		)
Amortization of unrecognized:
Prior service cost	0.3			0.2			0.2			0.1			0.1			—
Recognized net actuarial (gain)/loss	8.1			8.1			8.4			(0.1		)	(0.1		)	—
Net periodic benefit costs before regulatory adjustment	27.9			15.1			16.5			0.7			(0.2		)	0.8
Regulatory adjustment	2.6			2.8			0.7			(0.4		)	(0.4		)	0.1
Net periodic benefit costs	$	30.5		$	17.9		$	17.2		$	0.3		$	(0.6	)	$	0.9

	Pension Benefits									Post-Retirement Benefits
Year to Date September 30, 2018	Evergy			Westar Energy			KCP&L^(a)			Evergy			Westar Energy			KCP&L^(a)
Components of net periodic benefit costs	(millions)
Service cost	$	40.4		$	24.1		$	27.4		$	1.5		$	1.0		$	1.1
Interest cost	56.2			38.1			28.3			5.4			3.7			2.5
Expected return on plan assets	(59.3		)	(41.9		)	(31.7		)	(6.2		)	(5.2		)	(1.4		)
Amortization of unrecognized:
Prior service cost	0.6			0.5			0.4			0.3			0.3			—
Recognized net actuarial (gain)/loss	24.4			24.4			25.1			(0.4		)	(0.4		)	(0.1		)
Net periodic benefit costs before regulatory adjustment	62.3			45.2			49.5			0.6			(0.6		)	2.1
Regulatory adjustment	8.4			8.4			2.1			(1.3		)	(1.3		)	(0.2		)
Net periodic benefit costs	$	70.7		$	53.6		$	51.6		$	(0.7	)	$	(1.9	)	$	1.9

^(a)KCP&L amounts are included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.



	Pension Benefits									Post-Retirement Benefits
Three Months Ended September 30, 2017	Evergy			Westar Energy			KCP&L^(a)			Evergy			Westar Energy			KCP&L^(a)
Components of net periodic benefit costs	(millions)
Service cost	$	7.2		$	7.2		$	8.1		$	0.3		$	0.3		$	0.4
Interest cost	13.1			13.1			9.8			1.4			1.4			0.9
Expected return on plan assets	(13.4		)	(13.4		)	(9.5		)	(1.8		)	(1.8		)	(0.4		)
Amortization of unrecognized:
Prior service cost	0.1			0.1			0.2			0.1			0.1			—
Recognized net actuarial (gain)/loss	6.7			6.7			8.9			(0.2		)	(0.2		)	(0.1		)
Net periodic benefit costs before regulatory adjustment	13.7			13.7			17.5			(0.2		)	(0.2		)	0.8
Regulatory adjustment	3.6			3.6			0.2			(0.4		)	(0.4		)	(0.1		)
Net periodic benefit costs	$	17.3		$	17.3		$	17.7		$	(0.6	)	$	(0.6	)	$	0.7
^(a)KCP&L amounts are not included in consolidated Evergy for the three months ended September 30, 2017.

	Pension Benefits									Post-Retirement Benefits
Year to Date September 30, 2017	Evergy			Westar Energy			KCP&L^(a)			Evergy			Westar Energy			KCP&L^(a)
Components of net periodic benefit costs	(millions)
Service cost	$	21.5		$	21.5		$	24.4		$	0.9		$	0.9		$	1.1
Interest cost	39.3			39.3			29.4			4.2			4.2			2.8
Expected return on plan assets	(40.2		)	(40.2		)	(28.6		)	(5.2		)	(5.2		)	(1.3		)
Amortization of unrecognized:
Prior service cost	0.5			0.5			0.4			0.3			0.3			—
Recognized net actuarial (gain)/loss	20.2			20.2			26.7			(0.6		)	(0.6		)	(0.3		)
Net periodic benefit costs before regulatory adjustment	41.3			41.3			52.3			(0.4		)	(0.4		)	2.3
Regulatory adjustment	10.6			10.6			4.3			(1.4		)	(1.4		)	0.9
Net periodic benefit costs	$	51.9		$	51.9		$	56.6		$	(1.8	)	$	(1.8	)	$	3.2

^(a)KCP&L amounts are not included in consolidated Evergy for year to date September 30, 2017.

Equity Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Equity compensation expense and associated income tax benefits

The following table summarizes the Evergy Companies' equity compensation expense and the associated income tax (expense) benefit.



	Three Months Ended September 30					Year to Date September 30
	Three Months Ended September 30					Year to Date September 30
	2018			2017		2018			2017
Evergy	(millions)
Equity compensation expense	$	4.3		$	2.1	$	26.0		$	6.7
Income tax (expense) benefit	(1.5		)	0.8		1.9			2.6
Westar Energy
Equity compensation expense	$	2.0		$	2.1	$	22.6		$	6.7
Income tax (expense) benefit	(1.0		)	0.8		2.1			2.6
KCP&L^(a)
Equity compensation expense	$	1.6		$	1.2	$	4.8		$	2.9
Income tax (expense) benefit	(0.7		)	0.4		(0.1		)	1.2

^(a)KCP&L amounts are only included in consolidated Evergy from the date of the closing of the merger, June 4, 2018, through September 30, 2018.

Performance share activity

Performance share activity for year to date September 30, 2018 is summarized in the following table.



	Performance Shares			Grant Date Fair Value*
Beginning balance January 1, 2018		—			$	—
Converted Great Plains Energy awards upon merger		351,708			63.79
Forfeited		(3,212	)		63.44
Ending balance September 30, 2018		348,496			63.80

* weighted-average

Restricted stock activity

Restricted stock activity for year to date September 30, 2018 is summarized in the following table.



	Nonvested Restricted Stock			Grant Date Fair Value*
Beginning balance January 1, 2018		—			$	—
Converted Great Plains Energy awards upon merger		122,505			54.05
Vested		(4,222	)		54.50
Forfeited		(1,070	)		54.04
Ending balance September 30, 2018		117,213			54.03

* weighted-average

Restricted stock unit activity

RSU activity for awards with only service requirements for year to date September 30, 2018 is summarized in the following table.



	Nonvested Restricted Share Units			Grant Date Fair Value*
Beginning balance January 1, 2018		255,964			$	46.09
Granted		222,465			52.16
Converted Great Plains Energy awards upon merger		82,331			53.77
Vested		(342,599	)		46.81
Forfeited		(905	)		50.73
Ending balance September 30, 2018		217,256			54.07

* weighted-average

Short-term Borrowings and Short-term Bank Lines of Credit (Tables)

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Schedule of Short-term Debt [Table Text Block]

The following table summarizes the committed credit facilities (excluding receivable sale facilities) available to the Evergy Companies as of September 30, 2018 and December 31, 2017.



			Amounts Drawn
	Credit Facility		Commercial Paper		Letters of Credit		Cash Borrowings		Available Borrowings		Weighted Average Interest Rate on Short-Term Borrowings
September 30, 2018	(millions)
Evergy, Inc.	$	450.0	n/a		$	1.0	$	—	$	449.0	—%
Westar Energy	1,000.0		326.3		18.3		—		655.4		2.42%
KCP&L	600.0		209.2		2.7		—		388.1		2.50%
GMO	450.0		140.4		2.1		—		307.5		2.46%
Evergy	$	2,500.0	$	675.9	$	24.1	$	—	$	1,800.0

December 31, 2017
Westar Energy^(b)	$	979.3	$	275.7	$	11.8	$	—	$	691.8	1.83%
KCP&L^(a)	600.0		167.5		2.7		—		429.8		1.95%
Evergy	979.3		275.7		11.8		—		691.8		1.83%

^(a)KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

^(b)$20.7 million of Westar Energy's $730.0 million and $270.0 million revolving credit facilities expired in September 2017.

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Carrying value and fair value of debt instruments



	September 30, 2018				December 31, 2017
	Book Value		Fair Value		Book Value		Fair Value
Long-term debt^(a)	(millions)
Evergy^(b)	$	7,349.4	$	7,362.2	$	3,687.6	$	4,010.6
Westar Energy	3,689.7		3,750.8		3,687.6		4,010.6
KCP&L^(c)	2,529.9		2,611.3		2,582.2		2,799.1
Long-term debt of variable interest entities^(a)
Evergy	$	81.4	$	80.7	$	109.9	$	110.8
Westar Energy	81.4		80.7		109.9		110.8

^(a)Includes current maturities.

^(c)KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Fair value of assets and liabilities

The following tables include the Evergy Companies' balances of financial assets and liabilities measured at fair value on a recurring basis.



Description	September 30 2018			Level 1		Level 2			Level 3			NAV
Westar Energy		(millions)
Assets
Nuclear decommissioning trust^(a)
Domestic equity funds		$	80.9	$	74.7		$	—		$	—		$	6.2
International equity funds		42.3		42.3			—			—			—
Core bond fund		36.8		36.8			—			—			—
High-yield bond fund		20.1		20.1			—			—			—
Emerging markets bond fund		15.5		15.5			—			—			—
Combination debt/equity/other fund		14.8		14.8			—			—			—
Alternative investments fund		23.6		—			—			—			23.6
Real estate securities fund		11.5		—			—			—			11.5
Cash equivalents		0.3		0.3			—			—			—
Total nuclear decommissioning trust		245.8		204.5			—			—			41.3
Rabbi trust
Core bond fund		24.9		—			—			—			24.9
Combination debt/equity/other fund		6.2		—			—			—			6.2
Cash equivalents		0.1		0.1			—			—			—
Total rabbi trust		31.2		0.1			—			—			31.1
Total		$	277.0	$	204.6		$	—		$	—		$	72.4
KCP&L
Assets
Nuclear decommissioning trust^(a)
Equity securities		$	195.2	$	195.2		$	—		$	—		$	—
Debt securities
U.S. Treasury		39.5		39.5			—			—			—
U.S. Agency		0.4		—			0.4			—			—
State and local obligations		2.1		—			2.1			—			—
Corporate bonds		32.3		—			32.3			—			—
Foreign governments		0.1		—			0.1			—			—
Cash equivalents		1.5		1.5			—			—			—
Other		1.1		1.1			—			—			—
Total nuclear decommissioning trust		272.2		237.3			34.9			—			—
Self-insured health plan trust^(b)
Equity securities		0.5		0.5			—			—			—
Debt securities		3.1		0.3			2.8			—			—
Cash and cash equivalents		9.4		9.4			—			—			—
Total self-insured health plan trust		13.0		10.2			2.8			—			—
Total		$	285.2	$	247.5		$	37.7		$	—		$	—
Other Evergy
Assets
Rabbi trusts
Fixed income fund		$	13.5	$	—		$	—		$	—		$	13.5
Total rabbi trusts		$	13.5	$	—		$	—		$	—		$	13.5
Evergy
Assets
Nuclear decommissioning trust ^(a)		$	518.0	$	441.8		$	34.9		$	—		$	41.3
Rabbi trusts		44.7		0.1			—			—			44.6
Self-insured health plan trust ^(b)		13.0		10.2			2.8			—			—
Total		$	575.7	$	452.1		$	37.7		$	—		$	85.9



Description	December 31 2017			Level 1			Level 2			Level 3			NAV
Westar Energy		(millions)
Assets
Nuclear decommissioning trust^(a)(c)
Domestic equity funds		$	73.8		$	—		$	68.7		$	—		$	5.1
International equity funds		47.9			—			47.9			—			—
Core bond fund		33.3			—			33.3			—			—
High-yield bond fund		18.1			—			18.1			—			—
Emerging markets bond fund		17.3			—			17.3			—			—
Combination debt/equity/other fund		14.1			—			14.1			—			—
Alternative investments fund		21.7			—			—			—			21.7
Real estate securities fund		10.8			—			—			—			10.8
Cash equivalents		0.1			0.1			—			—			—
Total nuclear decommissioning trust		237.1			0.1			199.4			—			37.6
Rabbi trust^(c)
Core bond fund		27.3			—			27.3			—			—
Combination debt/equity/other fund		6.8			—			6.8			—			—
Cash equivalents		0.2			0.2			—			—			—
Total rabbi trust		34.3			0.2			34.1			—			—
Total		$	271.4		$	0.3		$	233.5		$	—		$	37.6
KCP&L^(d)
Assets
Nuclear decommissioning trust ^(a)
Equity securities		$	183.8		$	183.8		$	—		$	—		$	—
Debt securities
U.S. Treasury		35.3			35.3			—			—			—
U.S. Agency		0.4			—			0.4			—			—
State and local obligations		2.1			—			2.1			—			—
Corporate bonds		34.1			—			34.1			—			—
Foreign governments		0.1			—			0.1			—			—
Cash equivalents		2.5			2.5			—			—			—
Other		0.1			0.1			—			—			—
Total nuclear decommissioning trust		258.4			221.7			36.7			—			—
Self-insured health plan trust^(b)
Equity securities		0.5			0.5			—			—			—
Debt securities		2.7			0.3			2.4			—			—
Cash and cash equivalents		7.7			7.7			—			—			—
Total self-insured health plan trust		10.9			8.5			2.4			—			—
Total		$	269.3		$	230.2		$	39.1		$	—		$	—
Evergy
Assets
Nuclear decommissioning trust^(a)(c)		$	237.1		$	0.1		$	199.4		$	—		$	37.6
Rabbi trust^(c)		34.3			0.2			34.1			—			—
Total		$	271.4		$	0.3		$	233.5		$	—		$	37.6


^(a)	Fair value is based on quoted market prices of the investments held by the trust and/or valuation models.


^(b)	Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 1 are comprised of U.S. Treasury securities. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities.

^(c)


^(d)	KCP&L amounts are not included in consolidated Evergy as of December 31, 2017.

Fair value investments, entities that calculate NAV

The following table provides additional information on these Evergy and Westar Energy investments.



	September 30, 2018				December 31, 2017				September 30, 2018
	Fair		Unfunded		Fair		Unfunded		Redemption	Length of
	Value		Commitments		Value		Commitments		Frequency	Settlement
Westar Energy	(millions)
Nuclear decommissioning trust:
Domestic equity funds	$	6.2	$	4.8	$	5.1	$	2.8	(a)	(a)
Alternative investments fund^(b)	23.6		—		21.7		—		Quarterly	65 days
Real estate securities fund^(b)	11.5		—		10.8		—		Quarterly	65 days
Total	$	41.3	$	4.8	$	37.6	$	2.8
Rabbi trust:
Core bond fund	$	24.9	$	—	$	—	$	—	(c)	(c)
Combination debt/equity/other fund	6.2		—		—		—		(c)	(c)
Total	$	31.1	$	—	$	—	$	—
Other Evergy
Rabbi trusts:
Fixed income fund^(d)	$	13.5	$	—	$	—	$	—	(c)	(c)
Total Evergy investments at NAV	$	85.9	$	4.8	$	37.6	$	2.8

^(a)


^(b)	There is a holdback on final redemptions.


^(c)	This investment can be redeemed immediately and is not subject to any restrictions on redemptions.


^(d)	This investment is recorded at GMO. GMO amounts are not included in consolidated Evergy as of December 31, 2017.

Fair value recurring gain (loss) included in earnings

The following table summarizes the net unrealized gains (losses) for the Evergy Companies' nuclear decommissioning trusts and rabbi trusts.



	Three Months Ended September 30					Year to Date September 30
	2018			2017		2018			2017
Westar Energy	(millions)
Nuclear decommissioning trust - equity securities	$	6.5		$	7.7	$	(6.4	)	$	22.2
Rabbi trust	3.7			16.5		3.2			19.0
Total	$	10.2		$	24.2	$	(3.2	)	$	41.2
KCP&L^(a)
Nuclear decommissioning trust - equity securities	$	8.6		$	6.9	$	9.1		$	17.8
Nuclear decommissioning trust - debt securities	(0.5		)	—		(2.8		)	0.7
Total	$	8.1		$	6.9	$	6.3		$	18.5
Evergy
Nuclear decommissioning trust - equity securities	$	15.1		$	7.7	$	1.1		$	22.2
Nuclear decommissioning trust - debt securities	(0.5		)	—		(0.8		)	—
Rabbi trusts	3.7			16.5		3.1			19.0
Total	$	18.3		$	24.2	$	3.4		$	41.2

^(a)KCP&L amounts are only included in consolidated Evergy from the date of the merger, June 4, 2018 through September 30, 2018.

Related Party Transactions and Relationships (Tables)

9 Months Ended

Sep. 30, 2018

The following table summarizes Westar Energy's and KCP&L's related party net receivables and payables.



	September 30			December 31
	2018			2017
Westar Energy	(millions)
Net receivable from GMO	$	0.7		$	—
Net payable to KCP&L	(59.3		)	—
Net payable to Evergy	(14.6		)	—

KCP&L
Net receivable from GMO	$	63.3		$	65.8
Net receivable from Westar Energy	59.3			—
Net receivable from Evergy	16.4			—
Net receivable from Great Plains Energy	—			18.9

Variable Interest Entities (Tables)

9 Months Ended

Sep. 30, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Variable Interest Entities

The following table summarizes the assets and liabilities related to the VIE described above that are recorded on Evergy's and Westar Energy's consolidated balance sheets.



	September 30		December 31
	2018		2017
Assets:	(millions)
Property, plant and equipment of variable interest entities, net	$	170.9	$	176.3
Liabilities:
Current maturities of long-term debt of variable interest entities	$	30.3	$	28.5
Accrued interest^(a)	—		0.7
Long-term debt of variable interest entities, net	51.1		81.4


^(a)	Included in accrued interest on Evergy's and Westar Energy's consolidated balance sheets.

- Definition

Tabular disclosure of the significant judgments and assumptions made in determining whether a variable interest (as defined) held by the entity requires the variable interest entity (VIE) (as defined) to be consolidated and (or) disclose information about its involvement with the VIE, individually or in aggregate (as applicable); the nature of restrictions, if any, on the consolidated VIE's assets and on the settlement of its liabilities reported by an entity in its statement of financial position, including the carrying amounts of such assets and liabilities; the nature of, and changes in, the risks associated with involvement in the VIE; how involvement with the VIE affects the entity's financial position, financial performance, and cash flows; the lack of recourse if creditors (or beneficial interest holders) of the consolidated VIE have no recourse to the general credit of the primary beneficiary (if applicable); the terms of arrangements, giving consideration to both explicit arrangements and implicit variable interests, if any, that could require the entity to provide financial support to the VIE, including events or circumstances that could expose the entity to a loss; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; the significant factors considered and judgments made in determining that the power to direct the activities of a VIE that most significantly impact the VIE's economic performance are shared (as defined); the carrying amounts and classification of assets and liabilities of the VIE included in the statement of financial position; the entity's maximum exposure to loss, if any, as a result of its involvement with the VIE, including how the maximum exposure is determined and significant sources of the entity's exposure to the VIE; a comparison of the carrying amounts of the assets and liabilities and the entity's maximum exposure to loss; information about any liquidity arrangements, guarantees, and (or) other commitments by third parties that may affect the fair value or risk of the entity's variable interest in the VIE; whether or not the entity has provided financial support or other support (explicitly or implicitly) to the VIE that it was not previously contractually required to provide or whether the entity intends to provide that support, including the type and amount of the support and the primary reasons for providing the support; and supplemental information the entity determines necessary to provide.

+ References + Details

Taxes (Tables)

9 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

Components of income tax expense are detailed in the following tables.



Evergy
	Three Months Ended September 30						Year to Date September 30
	2018			2017			2018			2017
Current income taxes	(millions)
Federal	$	(30.3	)	$	(16.7	)	$	(21.5	)	$	(14.5	)
State	1.5			—			1.9			0.4
Total	(28.8		)	(16.7		)	(19.6		)	(14.1		)
Deferred income taxes
Federal	70.6			58.8			86.0			101.7
State	23.3			14.3			(35.7		)	27.0
Total	93.9			73.1			50.3			128.7
Investment tax credit amortization	(1.0		)	(0.6		)	(2.4		)	(2.0		)
Income tax expense	$	64.1		$	55.8		$	28.3		$	112.6



Westar Energy
	Three Months Ended September 30						Year to Date September 30
	2018			2017			2018			2017
Current income taxes	(millions)
Federal	$	8.0		$	(16.7	)	$	18.9		$	(14.5	)
State	(9.2		)	—			(6.7		)	0.4
Total	(1.2		)	(16.7		)	12.2			(14.1		)
Deferred income taxes
Federal	12.3			58.8			15.4			101.7
State	12.0			14.3			(47.6		)	27.0
Total	24.3			73.1			(32.2		)	128.7
Investment tax credit amortization	(0.7		)	(0.6		)	(2.0		)	(2.0		)
Income tax expense (benefit)	$	22.4		$	55.8		$	(22.0	)	$	112.6



KCP&L
	Three Months Ended September 30						Year to Date September 30
	2018			2017			2018			2017
Current income taxes	(millions)
Federal	$	20.7		$	41.8		$	43.5		$	56.2
State	6.8			7.6			11.6			10.2
Total	27.5			49.4			55.1			66.4
Deferred income taxes
Federal	(1.9		)	10.3			(23.4		)	27.2
State	2.7			2.8			49.4			6.2
Total	0.8			13.1			26.0			33.4
Investment tax credit amortization	(0.3		)	(0.3		)	(0.8		)	(0.8		)
Income tax expense	$	28.0		$	62.2		$	80.3		$	99.0

Schedule of Effective Income Tax Rate Reconciliation

Effective income tax rates reflected in the financial statements and the reasons for their differences from the statutory federal rates are detailed in the following tables.



Evergy
	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Federal statutory income tax rate	21.0	%	35.0	%	21.0	%	35.0	%
Effect of:
COLI policies	(2.4	)	(4.6	)	(2.4	)	(4.5	)
State income taxes	4.6		4.3		4.7		4.3
Flow through depreciation for plant-related differences	(1.5	)	2.3		(1.6	)	2.8
Federal tax credits	(7.5	)	(7.1	)	(7.5	)	(7.0	)
Non-controlling interest	(0.4	)	(0.5	)	(0.4	)	(0.8	)
AFUDC equity	(0.1	)	(0.2	)	(0.1	)	(0.2	)
Amortization of federal investment tax credits	(0.6	)	(0.6	)	(0.6	)	(0.6	)
State tax rate change	0.1		—		(9.5	)	—
Valuation allowance	—		—		0.4		—
Stock compensation	—		—		(0.5	)	(1.0	)
Officer compensation limitation	1.2		—		1.2		—
Other	0.8		(2.8	)	0.4		(0.7	)
Effective income tax rate	15.2	%	25.8	%	5.1	%	27.3	%



Westar Energy
	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Federal statutory income tax rate	21.0	%	35.0	%	21.0	%	35.0	%
Effect of:
COLI policies	(4.0	)	(4.6	)	(4.0	)	(4.5	)
State income taxes	1.1		4.3		3.3		4.3
Flow through depreciation for plant-related differences	1.5		2.3		0.3		2.8
Federal tax credits	(11.8	)	(7.1	)	(11.7	)	(7.0	)
Non-controlling interest	(0.6	)	(0.5	)	(0.7	)	(0.8	)
AFUDC equity	(0.1	)	(0.2	)	(0.1	)	(0.2	)
Amortization of federal investment tax credits	(0.8	)	(0.6	)	(0.8	)	(0.6	)
Changes in uncertain tax positions, net	0.1		—		0.1		—
State tax rate change	—		—		(17.7	)	—
Valuation allowance	—		—		0.6		—
Stock compensation	—		—		(0.9	)	(1.0	)
Officer compensation limitation	1.9		—		1.9		—
Other	2.9		(2.8	)	1.3		(0.7	)
Effective income tax rate	11.2	%	25.8	%	(7.4	)%	27.3	%



KCP&L
	Three Months Ended September 30				Year to Date September 30
	2018		2017		2018		2017
Federal statutory income tax rate	21.0	%	35.0	%	21.0	%	35.0	%
Effect of:
COLI policies	(0.2	)	(0.3	)	(0.2	)	(0.3	)
State income taxes	5.0		3.9		5.1		3.9
Flow through depreciation for plant-related differences	(4.9	)	0.1		(4.9	)	0.2
Federal tax credits	(1.9	)	(3.1	)	(1.8	)	(2.6	)
AFUDC equity	—		(0.7	)	(0.1	)	(0.7	)
Amortization of federal investment tax credits	(0.4	)	(0.4	)	(0.4	)	(0.4	)
State tax rate change	—		—		14.5		—
Valuation allowance	—		0.6		—		0.4
Stock compensation	—		0.1		—		0.2
Officer compensation limitation	0.7		—		0.5		—
Other	(0.4	)	0.1		(1.0	)	0.1
Effective income tax rate	18.9	%	35.3	%	32.7	%	35.8	%

Organization and Basis of Presentation - Organization (Details) customer in Millions	9 Months Ended
	Sep. 30, 2018 customer subsidiary Rate MW
Summary Of Accounting Policies [Line Items]
Owned generating capacity \| MW	12,300
Number of customers served \| customer	1.6
Kansas Gas And Electric Company [Member] \| Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Number of active wholly owned subsidiaries \| subsidiary	1
KCP&L Receivables Company [Member] \| KCPL [Member]
Summary Of Accounting Policies [Line Items]
Number of active wholly owned subsidiaries \| subsidiary	1
GMO Receivables Company [Member] \| KCPL Greater Missouri Operations [Member]
Summary Of Accounting Policies [Line Items]
Number of active wholly owned subsidiaries \| subsidiary	1
Transource Energy, LLC [Member] \| GPE Transmission Holding Company, LLC [Member]
Summary Of Accounting Policies [Line Items]
Ownership percentage \| Rate	13.50%
Transource Energy, LLC [Member] \| AEP Transmission Holding Company, LLC [Member]
Summary Of Accounting Policies [Line Items]
Ownership interest \| Rate	86.50%
Prairie Wind Transmission, LLC [Member] \| Westar Energy Inc [Member]
Summary Of Accounting Policies [Line Items]
Ownership percentage \| Rate	50.00%

Organization and Basis of Presentation - Summary of Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease in pension and post-retirement liability	$ (949.7)		$ (949.7)		$ (491.2)
Increase in other long-term liabilities	231.9		231.9		133.3
Amortization of deferred refueling outage			14.7	$ 12.1
Deferred income taxes, net	93.9	$ 73.1	50.3	128.7
Investment tax credit amortization	(1.0)	(0.6)	(2.4)	(2.0)
Net deferred income taxes and credits			47.8	127.0
Payments for asset retirement obligations			(15.9)	(1.9)
Other			(1.9)	(5.3)
Fuel inventory and supplies			44.6	15.5
Prepaid expenses and other current assets			(3.4)	55.5
Other current liabilities			38.9	(108.5)
Changes in other assets			26.0	22.9
Changes in other liabilities			33.9	5.5
Cash Flows from Operating Activities			1,191.6	742.7
Additions to property, plant and equipment			(698.3)	(564.6)
Other investing activities			(15.2)	(3.3)
Cash Flows from (used in) Investing Activities			574.8	(581.4)
Westar Energy Inc [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease in pension and post-retirement liability	(465.2)		(465.2)		(491.2)
Increase in other long-term liabilities	127.8		127.8		133.3
Amortization of deferred refueling outage			10.5	12.1
Deferred income taxes, net	24.3	73.1	(32.2)	128.7
Investment tax credit amortization	(0.7)	(0.6)	(2.0)	(2.0)
Net deferred income taxes and credits			(34.2)	127.0
Payments for asset retirement obligations			(10.6)	(1.9)
Other			(1.9)	(5.3)
Fuel inventory and supplies			25.4	15.5
Prepaid expenses and other current assets			(7.0)	55.5
Other current liabilities			23.2	(108.5)
Changes in other assets			22.9	22.9
Changes in other liabilities			(26.7)	5.5
Cash Flows from Operating Activities			707.2	742.7
Additions to property, plant and equipment			(510.3)	(564.6)
Other investing activities			(8.1)	(3.3)
Cash Flows from (used in) Investing Activities			(523.0)	(581.4)
Westar Energy Inc [Member] \| Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease in pension and post-retirement liability					50.2
Increase in other long-term liabilities					(50.2)
KCPL [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Decrease in pension and post-retirement liability	(522.3)		(522.3)		(512.2)
Increase in other long-term liabilities	80.7		80.7		$ 61.6
Amortization of deferred refueling outage			10.3	13.7
Deferred income taxes, net	0.8	13.1	26.0	33.4
Investment tax credit amortization	$ (0.3)	$ (0.3)	(0.8)	(0.8)
Net deferred income taxes and credits			25.2	32.6
Payments for asset retirement obligations			(9.9)	(14.9)
Other			2.7	6.3
Fuel inventory and supplies			13.2	3.6
Prepaid expenses and other current assets			(3.6)	8.9
Other current liabilities			8.5	9.9
Changes in other assets			28.3	52.6
Changes in other liabilities			79.0	7.3
Cash Flows from Operating Activities			504.5	526.6
Additions to property, plant and equipment			(310.6)	(317.1)
Other investing activities			3.4	0.8
Cash Flows from (used in) Investing Activities			$ (312.6)	(318.8)
KCPL [Member] \| As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of other				23.4
Amortization of deferred refueling outage				0.0
Deferred income taxes, net				33.4
Investment tax credit amortization				(0.8)
Net deferred income taxes and credits				0.0
Payments for asset retirement obligations				0.0
Other				(16.0)
Fuel inventory and supplies				0.0
Fuel inventories				10.8
Materials and supplies				(7.2)
Prepaid expenses and other current assets				0.0
Accrued interest				8.1
Other current liabilities				0.0
Changes in other assets				0.0
Changes in other liabilities				0.0
Deferred refueling outage costs				12.1
Pension and post-retirement benefit obligations				48.6
Fuel recovery mechanisms				7.6
Cash Flows from Operating Activities				120.0
Additions to property, plant and equipment				0.0
Utility capital expenditures				(295.1)
Allowance for borrowed funds used during construction				(4.2)
Other investing activities				(17.0)
Cash Flows from (used in) Investing Activities				(316.3)
KCPL [Member] \| Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Amortization of other				0.0
Amortization of deferred refueling outage				13.7
Deferred income taxes, net				0.0
Investment tax credit amortization				0.0
Net deferred income taxes and credits				32.6
Payments for asset retirement obligations				(14.9)
Other				6.3
Fuel inventory and supplies				3.6
Fuel inventories				0.0
Materials and supplies				0.0
Prepaid expenses and other current assets				8.9
Accrued interest				0.0
Other current liabilities				9.9
Changes in other assets				52.6
Changes in other liabilities				7.3
Deferred refueling outage costs				0.0
Pension and post-retirement benefit obligations				0.0
Fuel recovery mechanisms				0.0
Cash Flows from Operating Activities				120.0
Additions to property, plant and equipment				(317.1)
Utility capital expenditures				0.0
Allowance for borrowed funds used during construction				0.0
Other investing activities				0.8
Cash Flows from (used in) Investing Activities				$ (316.3)

Organization and Basis of Presentation - Fuel Inventory and Supplies (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Inventory [Line Items]
Fuel inventory	$ 163.1	$ 94.1
Supplies	357.8	199.5
Fuel inventory and supplies	520.9	293.6
Westar Energy Inc [Member]
Inventory [Line Items]
Fuel inventory	84.9	94.1
Supplies	183.8	199.5
Fuel inventory and supplies	268.7	293.6
KCPL [Member]
Inventory [Line Items]
Fuel inventory	54.6	71.0
Supplies	129.2	126.0
Fuel inventory and supplies	$ 183.8	$ 197.0

Organization and Basis of Presentation - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 18,836.0	$ 9,553.8
Electric Plant in Service [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	27,290.0	12,954.3
Property, plant and equipment, adjustment	740.6	739.0
Accumulated depreciation	(10,168.2)	(4,651.7)
Property, plant and equipment, net	17,862.4	9,041.6
Construction Work in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	723.5	434.9
Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	109.1	71.4
Plant to be Retired [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	141.0	5.9
Westar Energy Inc [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	9,637.5	9,553.8
Westar Energy Inc [Member] \| Electric Plant in Service [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	13,236.1	12,954.3
Property, plant and equipment, adjustment	740.6	739.0
Accumulated depreciation	(4,838.9)	(4,651.7)
Property, plant and equipment, net	9,137.8	9,041.6
Westar Energy Inc [Member] \| Construction Work in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	443.6	434.9
Westar Energy Inc [Member] \| Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	54.1	71.4
Westar Energy Inc [Member] \| Plant to be Retired [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	2.0	5.9
KCPL [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	6,660.3	6,565.6
KCPL [Member] \| Electric Plant in Service [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,594.2	10,213.2
Property, plant and equipment, adjustment	0.0	0.0
Accumulated depreciation	(4,172.3)	(4,070.3)
Property, plant and equipment, net	6,421.9	6,142.9
KCPL [Member] \| Construction Work in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	183.4	350.3
KCPL [Member] \| Nuclear Fuel [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	55.0	72.4
KCPL [Member] \| Plant to be Retired [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, net	$ 0.0	$ 0.0

Organization and Basis of Presentation - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income
Net income	$ 357.6	$ 160.7	$ 524.9	$ 300.2
Less: Net income attributable to noncontrolling interests	2.6	2.4	7.6	10.2
NET INCOME	355.0	158.3	517.3	290.0
Less: net income allocated to RSUs	0.2	0.3	0.4	0.5
Net income allocated to common stock	$ 354.8	$ 158.0	$ 516.9	$ 289.5
Common Shares Outstanding
Weighted average equivalent common shares outstanding - basic (in shares)	268.6	142.5	197.9	142.5
Add: effect of dilutive securities (in shares)	0.2	0.0	0.1	0.0
Weighted average equivalent common shares outstanding - diluted (in shares)	268.8	142.5	198.0	142.5
Basic and Diluted EPS
Basic and Diluted EPS (in dollars per share)	$ 1.32	$ 1.11	$ 2.61	$ 2.03

Organization and Basis of Presentation - Antidilutive Securities (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	0	0	0

Organization and Basis of Presentation Organization and Basis of Presentation - Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Millions		9 Months Ended
	Nov. 07, 2018	Sep. 30, 2018	Sep. 30, 2017
Dividends Payable [Line Items]
Dividends declared on common stock (in dollars per share)		$ 1.26	$ 1.20
Subsequent Event [Member]
Dividends Payable [Line Items]
Dividends declared on common stock (in dollars per share)	$ 0.475
Westar Energy Inc [Member]
Dividends Payable [Line Items]
Dividends declared on common stock (in dollars per share)			$ 1.20
Westar Energy Inc [Member] \| Subsequent Event [Member]
Dividends Payable [Line Items]
Dividends Payable	$ 70.0

Organization and Basis of Presentation - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash paid for (received from):
Interest, net of amounts capitalized	$ 148.7	$ 109.0
Income taxes, net of refunds	0.6	(12.6)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(24.8)	112.5
Deconsolidation of property, plant and equipment of VIE	0.0	(72.9)
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	0.4	4.9
Non-cash financing, deconsolidation of VIE	0.0	(83.1)
Assets acquired through capital leases	0.1	4.6
Variable Interest Entities [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	2.3	3.1
Westar Energy Inc [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	110.5	109.0
Income taxes, net of refunds	0.0	(12.6)
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	(42.0)	112.5
Deconsolidation of property, plant and equipment of VIE	0.0	(72.9)
Non-cash financing transactions:
Issuance of stock for compensation and reinvested dividends	0.0	4.9
Non-cash financing, deconsolidation of VIE	0.0	(83.1)
Assets acquired through capital leases	0.1	4.6
Westar Energy Inc [Member] \| Variable Interest Entities [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	2.3	3.1
KCPL [Member]
Cash paid for (received from):
Interest, net of amounts capitalized	87.6	88.6
Income taxes, net of refunds	28.4	4.9
Non-cash investing transactions:
Property, plant and equipment additions (reductions)	$ 15.2	$ 15.5

Organization and Basis of Presentation - Schedule of Retrospective Adjustments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense	$ 330.4	$ 140.6	$ 754.2	$ 415.6
Total operating expenses	1,049.4	529.4	2,292.6	1,419.7
Income from operations	533.1	264.9	783.5	556.5
Other expense	(30.8)	(11.5)	(55.2)	(29.6)
Total other income (expense), net	(24.3)	(6.6)	(43.7)	(20.4)
As Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense		145.5		430.6
Total operating expenses		534.3		1,434.7
Income from operations		260.0		541.5
Other expense		(6.6)		(14.6)
Total other income (expense), net		(1.7)		(5.4)
Accounting Standards Update 2017-07 [Member] \| Effect of Change [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense		(4.9)		(15.0)
Total operating expenses		(4.9)		(15.0)
Income from operations		4.9		15.0
Other expense		(4.9)		(15.0)
Total other income (expense), net		(4.9)		(15.0)
Westar Energy Inc [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense	141.7	140.6	491.4	415.6
Total operating expenses	507.9	529.4	1,559.4	1,419.7
Income from operations	256.9	264.9	456.5	556.5
Other expense	(15.2)	(11.5)	(36.1)	(29.6)
Total other income (expense), net	(13.9)	(6.6)	(31.6)	(20.4)
Westar Energy Inc [Member] \| As Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense		145.5		430.6
Total operating expenses		534.3		1,434.7
Income from operations		260.0		541.5
Other expense		(6.6)		(14.6)
Total other income (expense), net		(1.7)		(5.4)
Westar Energy Inc [Member] \| Accounting Standards Update 2017-07 [Member] \| Effect of Change [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense		(4.9)		(15.0)
Total operating expenses		(4.9)		(15.0)
Income from operations		4.9		15.0
Other expense		(4.9)		(15.0)
Total other income (expense), net		(4.9)		(15.0)
KCPL [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense	127.3	114.3	354.5	350.7
Total operating expenses	370.2	375.9	1,043.8	1,058.1
Income from operations	189.4	219.8	365.1	416.2
Other expense	(9.0)	(11.9)	(22.9)	(40.7)
Total other income (expense), net	$ (8.1)	(9.2)	$ (19.1)	(33.8)
KCPL [Member] \| As Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense		124.2		385.0
Total operating expenses		385.8		1,092.4
Income from operations		209.9		381.9
Other expense		(2.0)		(6.4)
Total other income (expense), net		0.7		0.5
KCPL [Member] \| Accounting Standards Update 2017-07 [Member] \| Effect of Change [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating and maintenance expense		(9.9)		(34.3)
Total operating expenses		(9.9)		(34.3)
Income from operations		9.9		34.3
Other expense		(9.9)		(34.3)
Total other income (expense), net		$ (9.9)		$ (34.3)

Organization and Basis of Presentation - New Accounting Standards (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flows provided by (used in) operating activities			$ 1,191.6	$ 742.7
Cash flows provided by (used in) investing activities			574.8	(581.4)
Cash, cash equivalents and restricted cash	$ 679.8	$ 3.5	679.8	3.5	$ 3.5	$ 3.2
Operating revenues	(1,582.5)	(794.3)	(3,076.1)	(1,976.2)
Taxes other than income tax	(83.0)	(41.8)	(183.5)	(126.4)
Accounting Standards Update 2016-15 - Corporate Owned Life Insurance, Premiums [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flows provided by (used in) operating activities				2.3
Cash flows provided by (used in) investing activities				(2.3)
Accounting Standards Update 2016-15 - Corporate Owned Life Insurance, Settlements [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flows provided by (used in) operating activities				(1.9)
Cash flows provided by (used in) investing activities				1.9
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash, cash equivalents and restricted cash		0.1		0.1		0.1
Westar Energy Inc [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flows provided by (used in) operating activities			707.2	742.7
Cash flows provided by (used in) investing activities			(523.0)	(581.4)
Cash, cash equivalents and restricted cash	3.4	3.5	3.4	3.5	$ 3.5	3.2
Operating revenues	(764.8)	(794.3)	(2,015.9)	(1,976.2)
Taxes other than income tax	(42.2)	(41.8)	(128.8)	(126.4)
Westar Energy Inc [Member] \| Accounting Standards Update 2016-15 - Corporate Owned Life Insurance, Premiums [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flows provided by (used in) operating activities				2.3
Cash flows provided by (used in) investing activities				(2.3)
Westar Energy Inc [Member] \| Accounting Standards Update 2016-15 - Corporate Owned Life Insurance, Settlements [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash flows provided by (used in) operating activities				(1.9)
Cash flows provided by (used in) investing activities				1.9
Westar Energy Inc [Member] \| Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash, cash equivalents and restricted cash		$ 0.1		$ 0.1		$ 0.1
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating revenues	22.1		59.7
Taxes other than income tax	$ 22.1		$ 59.7

Merger of Great Plains Energy and Westar Energy - Narrative (Details) $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 04, 2018	May 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Acquisition-related Costs [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
Merger-related costs			$ 5.2	$ 6.0	$ 73.4	$ 9.4
Merger Settlement Agreement [Member] \| Kansas Corporation Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		$ 30.6
Additional bill credits		46.0
Additional bill credits, annual amount		11.5
Merger-related savings on current rate cases		$ 30.0
Base rate moratorium period		5 years
Return on equity refund		50.00%
Charitable contributions period		5 years
Merger transaction costs, recovery amount		$ 30.9
Merger transaction costs, recovery period		10 years
Merger Settlement Agreement [Member] \| Missouri Public Service Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		$ 29.1
Charitable contributions period		5 years
Merger transaction costs, recovery amount		$ 16.9
Merger transaction costs, recovery period		10 years
One-time bill credits, period		120 days
Support to promote low-income weatherization, amount		$ 3.0
Support to promote low-income weatherization, period		10 years
Westar Energy Inc [Member] \| Merger Settlement Agreement [Member] \| Kansas Corporation Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		$ 23.1
Additional bill credits, annual amount		8.7
Merger-related savings on current rate cases		22.5
Merger transaction costs, recovery amount		23.2
KCPL [Member] \| Merger Settlement Agreement [Member] \| Kansas Corporation Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		7.5
Additional bill credits, annual amount		2.8
Merger-related savings on current rate cases		7.5
Merger transaction costs, recovery amount		7.7
KCPL [Member] \| Merger Settlement Agreement [Member] \| Missouri Public Service Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		14.9
Merger transaction costs, recovery amount		9.7
KCPL Greater Missouri Operations [Member] \| Merger Settlement Agreement [Member] \| Missouri Public Service Commission [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
One-time bill credits		14.2
Merger transaction costs, recovery amount		$ 7.2
Westar Energy Inc [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
Conversion ratio	1
Great Plains Energy [Member]
Anticipated Merger With Westar Energy, Inc. [Line Items]
Earnings or Loss of Acquiree since Acquisition Date, Actual			178.8		239.0
Conversion ratio	0.5981
Revenue of acquiree since acquisition			817.6		1,060.2
Merger-related costs			$ 10.3	$ 7.9	$ 134.3	$ 8.9

Merger of Great Plains Energy and Westar Energy - Schedule of Pre-tax Costs and Deferrals (Details) - Great Plains Energy [Member] $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Business Acquisition [Line Items]
One-time bill credits	$ (59.7)
Annual bill credits	(7.6)
Total impact to operating revenues	(67.3)
Charitable contributions and community support	24.7
Voluntary severance and accelerated equity compensation	40.7
Other transaction and transition costs	47.0
Reallocation and deferral of merger transition costs	(47.8)
Total impact to operating and maintenance expense	64.6
Total	(131.9)
Westar Energy Inc [Member]
Business Acquisition [Line Items]
One-time bill credits	(23.1)
Annual bill credits	(5.8)
Total impact to operating revenues	(28.9)
Charitable contributions and community support	0.0
Voluntary severance and accelerated equity compensation	40.7
Other transaction and transition costs	20.4
Reallocation and deferral of merger transition costs	(13.3)
Total impact to operating and maintenance expense	47.8
Total	(76.7)
KCPL [Member]
Business Acquisition [Line Items]
One-time bill credits	(22.4)
Annual bill credits	(1.9)
Total impact to operating revenues	(24.3)
Charitable contributions and community support	0.0
Voluntary severance and accelerated equity compensation	0.0
Other transaction and transition costs	1.7
Reallocation and deferral of merger transition costs	(23.9)
Total impact to operating and maintenance expense	(22.2)
Total	$ (2.1)

Merger of Great Plains Energy and Westar Energy - Purchase Price Allocation (Details) $ / shares in Units, $ in Millions	Jun. 04, 2018 USD ($) $ / shares shares
Business Acquisition [Line Items]
Common stock outstanding (in shares)	215,800,074
Awards outstanding (in shares)	(204,825)
Great Plains Energy shares to be converted to Evergy shares (in shares)	215,595,249
Great Plains Energy [Member]
Business Acquisition [Line Items]
Exchange ratio	0.5981
Number of shares issued (in shares)	128,947,518
Closing price (in dollars per share) \| $ / shares	$ 54.00
Total purchase price \| $	$ 6,975.7
Common Stock [Member] \| Great Plains Energy [Member]
Business Acquisition [Line Items]
Fair value of shares issued \| $	6,963.2
Stock Compensation Plan [Member] \| Great Plains Energy [Member]
Business Acquisition [Line Items]
Fair value of shares issued \| $	$ 12.5

Merger of Great Plains Energy and Westar Energy - Schedule Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 04, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 2,333.5		$ 0.0
Great Plains Energy [Member]
Business Acquisition [Line Items]
Current assets		$ 2,151.7
Property, plant and equipment, net		9,179.7
Goodwill		2,333.5
Other long-term assets, excluding goodwill		1,235.9
Total assets		14,900.8
Current liabilities		1,673.9
Long-term liabilities, excluding long-term debt		2,892.6
Long-term debt, net		3,358.6
Total liabilities		7,925.1
Total purchase price		$ 6,975.7

Merger of Great Plains Energy and Westar Energy - Unaudited Pro Forma Financial Information (Details) - Great Plains Energy [Member] - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Operating revenues	$ 1,582.5	$ 1,651.5	$ 4,134.8	$ 4,086.7
Net income attributable to Evergy, Inc.	$ 360.2	$ 321.8	$ 694.5	$ 543.3
Basic earnings per common share (in dollars per share)	$ 1.34	$ 1.19	$ 2.56	$ 2.00
Diluted earnings per common share (in dollars per share)	$ 1.34	$ 1.19	$ 2.55	$ 2.00

Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,567.0		$ 3,051.4
Other	15.5		24.7
Operating revenues	1,582.5	$ 794.3	3,076.1	$ 1,976.2
Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	761.3		2,011.8
Other	3.5		4.1
Operating revenues	764.8	794.3	2,015.9	1,976.2
KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	550.8		1,360.2
Other	8.8		48.7
Operating revenues	559.6	$ 595.7	1,408.9	$ 1,474.3
Electric Utility Customer Class Residential [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	647.1		1,169.4
Electric Utility Customer Class Residential [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	270.5		671.9
Electric Utility Customer Class Residential [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	243.5		585.4
Electric Utility Customer Class Commercial [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	530.5		945.0
Electric Utility Customer Class Commercial [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	217.4		542.8
Electric Utility Customer Class Commercial [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	231.1		609.2
Electric Utility Customer Class Industrial [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	173.4		375.5
Electric Utility Customer Class Industrial [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	111.9		297.2
Electric Utility Customer Class Industrial [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	39.1		105.4
Electric Utility Customer Class Other Retail [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	10.9		21.5
Electric Utility Customer Class Other Retail [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5.4		15.3
Electric Utility Customer Class Other Retail [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	2.7		7.7
Electric Utility Customer Class Total Electric Retail [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1,361.9		2,511.4
Electric Utility Customer Class Total Electric Retail [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	605.2		1,527.2
Electric Utility Customer Class Total Electric Retail [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	516.4		1,307.7
Electric Utility Customer Class Wholesale [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	118.5		302.4
Electric Utility Customer Class Wholesale [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	82.4		263.7
Electric Utility Customer Class Wholesale [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	29.9		38.5
Electric Utility Customer Class Transmission [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	80.6		227.6
Electric Utility Customer Class Transmission [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	72.2		216.3
Electric Utility Customer Class Transmission [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3.8		11.0
Electric Utility Customer Class Industrial Steam [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	6.0		10.0
Electric Utility Customer Class Industrial Steam [Member] \| Westar Energy Inc [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	1.5		4.6
Electric Utility Customer Class Industrial Steam [Member] \| KCPL [Member]
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 0.7		$ 3.0

Receivables (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	$ 82.4	$ 55.4
Total	496.5	290.7
Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	60.7	55.4
Total	347.5	290.7
KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other receivables	14.5	39.3
Total	102.9	106.3
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts	(8.7)	(6.7)
Trade Accounts Receivable [Member] \| Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts	(3.9)	(6.7)
Trade Accounts Receivable [Member] \| KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts	(3.5)	(2.2)
Trade Accounts Receivable [Member] \| Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	231.7	165.4
Trade Accounts Receivable [Member] \| Billed Revenues [Member] \| Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	194.0	165.4
Trade Accounts Receivable [Member] \| Billed Revenues [Member] \| KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	25.3	1.6
Trade Accounts Receivable [Member] \| Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	191.1	76.6
Trade Accounts Receivable [Member] \| Unbilled Revenues [Member] \| Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	96.7	76.6
Trade Accounts Receivable [Member] \| Unbilled Revenues [Member] \| KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Customer accounts receivable	$ 66.6	$ 67.6

Receivables - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Other receivables, contracts with customers	$ 57.7
Sale Of Accounts Receivable - KCPL and GMO
Accounts receivable pledged as collateral	195.0	$ 0.0
Collateralized note payable	195.0	0.0
Westar Energy Inc [Member]
Other receivables, contracts with customers	52.8
KCPL [Member]
Other receivables, contracts with customers	1.0
Sale Of Accounts Receivable - KCPL and GMO
Accounts receivable pledged as collateral	130.0	130.0
Collateralized note payable	130.0	$ 130.0
Maximum amount of outstanding principal under receivables agreement	130.0
KCPL Greater Missouri Operations [Member]
Sale Of Accounts Receivable - KCPL and GMO
Maximum amount of outstanding principal under receivables agreement from mid-November to mid-June	50.0
Maximum amount of outstanding principal under receivables agreement from mid-June to mid-November	$ 65.0

Receivables - Summary of Bad Debt Expense (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	$ 4.5	$ 2.0	$ 10.6	$ 5.4
Westar Energy Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	1.1	2.0	6.2	5.4
KCPL [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impairment losses recognized on receivables	$ 3.9	$ 2.8	$ 7.5	$ 6.0

Rate Matters and Regulation (Details) - USD ($) $ in Millions	1 Months Ended						9 Months Ended
	Oct. 31, 2018	Sep. 30, 2018	May 31, 2018	Mar. 31, 2018	Feb. 28, 2018	Jan. 31, 2018	Sep. 30, 2018
Transmission Delivery Charge [Member] \| Westar Energy Inc [Member] \| Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved				$ 31.5
2018 Rate Case Proceedings [Member] \| Westar Energy Inc [Member] \| Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), requested					$ (2.0)
Revised annual revenue increase, requested					$ 54.0
Return on equity, requested					9.85%
Return on equity, approved		9.30%
Rate-making equity ratio, requested					51.60%
Rate-making equity ratio, approved		51.46%
Annual revenue increase (decrease) related to rebasing, approved		$ 16.0
Increase (decrease) in depreciation expense, approved		46.0
Recovery of wholesale contract, approved		41.0
One-time bill credit, approved		50.0
Annual revenue increase (decrease), approved, not including rebasing		(66.0)
2018 Rate Case Proceedings [Member] \| KCPL Greater Missouri Operations [Member] \| Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Return on equity, requested						9.85%
Rate-making equity ratio, requested						54.40%
Annual revenue increase (decrease) related to rebasing, requested						$ 21.7
Annual revenue increase (decrease), requested, not including rebasing						$ (2.4)
2018 Rate Case Proceedings [Member] \| KCPL [Member] \| Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Return on equity, requested						9.85%
Rate-making equity ratio, requested						50.03%
Annual revenue increase (decrease) related to rebasing, requested						$ 7.5
Annual revenue increase (decrease), requested, not including rebasing						8.9
2018 Rate Case Proceedings [Member] \| KCPL [Member] \| Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Return on equity, requested			9.85%
Rate-making equity ratio, requested			49.80%
Annual revenue increase (decrease) related to rebasing, requested			$ 6.7
Annual revenue increase (decrease), requested, not including rebasing			$ 26.2
FERC Proceedings [Member] \| Westar Energy Inc [Member] \| Federal Energy Regulatory Commission [Member]
Regulatory Proceedings [Line Items]
Regulatory liability		$ 5.9					$ 5.9
Annual transmissions revenue estimated amount of increase (decrease) over prior year						$ 25.5	$ 2.3
Subsequent Event [Member] \| Transmission Delivery Charge [Member] \| Westar Energy Inc [Member] \| Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved	$ (20.0)
Subsequent Event [Member] \| 2018 Rate Case Proceedings [Member] \| KCPL Greater Missouri Operations [Member] \| Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved	(24.0)
One-time bill credit, approved	29.3
Subsequent Event [Member] \| 2018 Rate Case Proceedings [Member] \| KCPL [Member] \| Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase (decrease), approved	(21.1)
One-time bill credit, approved	38.7
Subsequent Event [Member] \| 2018 Rate Case Proceedings [Member] \| KCPL [Member] \| Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
One-time bill credit, requested	(36.9)
Public Utilities, Requested Rate Increase (Decrease) Following Stipulation, Amount	$ (10.7)
Public Utilities, Requested Return on Equity Following Stipulation	9.30%
Public Utilities, Requested Rate-Making Equity Ratio Following Stipulation	49.09%
Subsequent Event [Member] \| FERC 2019 TFR Proceeding [Member] \| Westar Energy Inc [Member] \| Federal Energy Regulatory Commission [Member]
Regulatory Proceedings [Line Items]
Annual transmissions revenue estimated amount of increase (decrease) over prior year	$ (11.2)

Asset Retirement Obligations (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance, January 1	$ 405.1	$ 405.1	$ 324.0
Liabilities assumed upon merger with Great Plains Energy		412.2	0.0
Liabilities incurred during the year		7.4	13.5
Revision in timing and/or estimates	(127.0)	(138.6)	66.8
Settlements		(15.9)	(16.0)
Accretion		22.1	16.8
Ending balance		692.3	405.1
Less: current portion		(69.6)	(25.1)
Total noncurrent asset retirement obligation		622.7	380.0
Wolf Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Jointly owned utility plant, proportionate ownership share				94.00%
Westar Energy Inc [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance, January 1	405.1	405.1	324.0
Liabilities assumed upon merger with Great Plains Energy		0.0	0.0
Liabilities incurred during the year		7.4	13.5
Revision in timing and/or estimates	(127.0)	(133.0)	66.8
Settlements		(10.6)	(16.0)
Accretion		14.0	16.8
Ending balance		282.9	405.1
Less: current portion		(25.1)	(25.1)
Total noncurrent asset retirement obligation		257.8	380.0
Westar Energy Inc [Member] \| Wolf Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Jointly owned utility plant, proportionate ownership share				47.00%	47.00%
KCPL [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance, January 1	$ 266.3	266.3	278.0
Liabilities assumed upon merger with Great Plains Energy		0.0	0.0
Liabilities incurred during the year		0.0	0.0
Revision in timing and/or estimates		(5.7)	0.3
Settlements		(9.9)	(25.5)
Accretion		12.6	13.5
Ending balance		263.3	266.3
Less: current portion		(40.6)	(34.9)
Total noncurrent asset retirement obligation		$ 222.7	$ 231.4
KCPL [Member] \| Wolf Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Jointly owned utility plant, proportionate ownership share				47.00%

Pension Plans and Other Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2018
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit costs [Abstract]
Service cost	$ 20.2	$ 7.2	$ 40.4	$ 21.5
Interest cost	26.3	13.1	56.2	39.3
Expected return on plan assets	(27.0)	(13.4)	(59.3)	(40.2)
Prior service cost	0.3	0.1	0.6	0.5
Recognized net actuarial (gain)/loss	8.1	6.7	24.4	20.2
Net periodic benefit costs before regulatory adjustment	27.9	13.7	62.3	41.3
Regulatory adjustment	2.6	3.6	8.4	10.6
Net periodic benefit costs	30.5	17.3	70.7	51.9
Contributions by employer			53.1
Contributions by employer, remainder of fiscal year	66.3		66.3
Pension Plans, Defined Benefit [Member] \| Westar Energy Inc [Member]
Components of net periodic benefit costs [Abstract]
Service cost	8.0	7.2	24.1	21.5
Interest cost	12.7	13.1	38.1	39.3
Expected return on plan assets	(13.9)	(13.4)	(41.9)	(40.2)
Prior service cost	0.2	0.1	0.5	0.5
Recognized net actuarial (gain)/loss	8.1	6.7	24.4	20.2
Net periodic benefit costs before regulatory adjustment	15.1	13.7	45.2	41.3
Regulatory adjustment	2.8	3.6	8.4	10.6
Net periodic benefit costs	17.9	17.3	53.6	51.9
Contributions by employer			43.1
Contributions by employer, remainder of fiscal year	4.9		4.9
Pension Plans, Defined Benefit [Member] \| KCPL [Member]
Components of net periodic benefit costs [Abstract]
Service cost	9.1	8.1	27.4	24.4
Interest cost	9.4	9.8	28.3	29.4
Expected return on plan assets	(10.6)	(9.5)	(31.7)	(28.6)
Prior service cost	0.2	0.2	0.4	0.4
Recognized net actuarial (gain)/loss	8.4	8.9	25.1	26.7
Net periodic benefit costs before regulatory adjustment	16.5	17.5	49.5	52.3
Regulatory adjustment	0.7	0.2	2.1	4.3
Net periodic benefit costs	17.2	17.7	51.6	56.6
Contributions by employer			23.7
Contributions by employer, remainder of fiscal year	61.4		61.4
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of net periodic benefit costs [Abstract]
Service cost	0.7	0.3	1.5	0.9
Interest cost	2.5	1.4	5.4	4.2
Expected return on plan assets	(2.5)	(1.8)	(6.2)	(5.2)
Prior service cost	0.1	0.1	0.3	0.3
Recognized net actuarial (gain)/loss	(0.1)	(0.2)	(0.4)	(0.6)
Net periodic benefit costs before regulatory adjustment	0.7	(0.2)	0.6	(0.4)
Regulatory adjustment	(0.4)	(0.4)	(1.3)	(1.4)
Net periodic benefit costs	0.3	(0.6)	(0.7)	(1.8)
Contributions by employer, remainder of fiscal year	4.6		4.6
Other Postretirement Benefit Plans, Defined Benefit [Member] \| Westar Energy Inc [Member]
Components of net periodic benefit costs [Abstract]
Service cost	0.4	0.3	1.0	0.9
Interest cost	1.2	1.4	3.7	4.2
Expected return on plan assets	(1.8)	(1.8)	(5.2)	(5.2)
Prior service cost	0.1	0.1	0.3	0.3
Recognized net actuarial (gain)/loss	(0.1)	(0.2)	(0.4)	(0.6)
Net periodic benefit costs before regulatory adjustment	(0.2)	(0.2)	(0.6)	(0.4)
Regulatory adjustment	(0.4)	(0.4)	(1.3)	(1.4)
Net periodic benefit costs	(0.6)	(0.6)	(1.9)	(1.8)
Other Postretirement Benefit Plans, Defined Benefit [Member] \| KCPL [Member]
Components of net periodic benefit costs [Abstract]
Service cost	0.4	0.4	1.1	1.1
Interest cost	0.8	0.9	2.5	2.8
Expected return on plan assets	(0.4)	(0.4)	(1.4)	(1.3)
Prior service cost	0.0	0.0	0.0	0.0
Recognized net actuarial (gain)/loss	0.0	(0.1)	(0.1)	(0.3)
Net periodic benefit costs before regulatory adjustment	0.8	0.8	2.1	2.3
Regulatory adjustment	0.1	(0.1)	(0.2)	0.9
Net periodic benefit costs	0.9	$ 0.7	1.9	$ 3.2
Contributions by employer, remainder of fiscal year	$ 4.6		$ 4.6
Wolf Creek [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share					94.00%
Wolf Creek [Member] \| Westar Energy Inc [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share					47.00%	47.00%
Wolf Creek [Member] \| KCPL [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly owned utility plant, proportionate ownership share					47.00%

Equity Compensation (Details) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Jun. 04, 2018 USD ($) shares	Sep. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2018 USD ($) $ / shares Rate shares	Sep. 30, 2017 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost \| $				$ 14.6
Equity compensation expense \| $		$ 4.3	$ 2.1	26.0	$ 6.7
Income tax (expense) benefit \| $		$ (1.5)	$ 0.8	$ 1.9	$ 2.6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Ending balance (in shares)	204,825
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)				255,964
Granted (in shares)		0	0	222,465
Converted Great Plains Energy award upon merger (in shares)				82,331
Vested (in shares)		0		(342,599)
Forfeited (in shares)				(905)
Ending balance (in shares)		217,256		217,256
Weighted average beginning balance (in dollars per share) \| $ / shares				$ 46.09
Weighted average granted (in dollars per share) \| $ / shares				52.16	$ 53.25
Weighted average converted (in dollars per share) \| $ / shares				53.77
Weighted average vested (in dollars per share) \| $ / shares				46.81
Weighted average forfeited (in dollars per share) \| $ / shares				50.73
Weighted average ending balance (in dollars per share) \| $ / shares		$ 54.07		$ 54.07
Total unrecognized compensation expense \| $		$ 9.5		$ 9.5
Total fair value of shares vested \| $			$ 0.2	$ 16.0	$ 3.8
Remaining weighted-average contractual term (in years)				1 year 8 months 15 days
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum (in hundredths) \| Rate				16.60%
Expected volatility, maximum (in hundredths) \| Rate				18.50%
Expected dividend yield (in hundredths) \| Rate				2.96%
Risk-free interest rate, minimum (in hundredths) \| Rate				1.80%
Risk-free interest rate, maximum (in hundredths) \| Rate				2.60%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)				0
Granted (in shares)		0	0
Converted Great Plains Energy award upon merger (in shares)				351,708
Forfeited (in shares)				(3,212)
Ending balance (in shares)		348,496		348,496
Weighted average beginning balance (in dollars per share) \| $ / shares				$ 0.00
Weighted average granted (in dollars per share) \| $ / shares				63.79
Weighted average converted (in dollars per share) \| $ / shares				63.79
Weighted average forfeited (in dollars per share) \| $ / shares				63.44
Weighted average ending balance (in dollars per share) \| $ / shares		$ 63.80		$ 63.80
Total unrecognized compensation expense \| $		$ 10.6		$ 10.6
Remaining weighted-average contractual term (in years)				1 year 3 months 20 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)				0
Granted (in shares)		0	0
Converted Great Plains Energy award upon merger (in shares)				122,505
Vested (in shares)				(4,222)
Forfeited (in shares)				(1,070)
Ending balance (in shares)		117,213		117,213
Weighted average beginning balance (in dollars per share) \| $ / shares				$ 0.00
Weighted average granted (in dollars per share) \| $ / shares				54.05
Weighted average converted (in dollars per share) \| $ / shares				54.05
Weighted average vested (in dollars per share) \| $ / shares				54.50
Weighted average forfeited (in dollars per share) \| $ / shares				54.04
Weighted average ending balance (in dollars per share) \| $ / shares		$ 54.03		$ 54.03
Total unrecognized compensation expense \| $		$ 3.1		$ 3.1
Total fair value of shares vested \| $		0.2		$ 0.2
Remaining weighted-average contractual term (in years)				1 year 4 months 26 days
Westar Energy Inc [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost \| $				$ 14.6
Equity compensation expense \| $		2.0	$ 2.1	22.6	6.7
Income tax (expense) benefit \| $		(1.0)	0.8	2.1	2.6
KCPL [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity compensation expense \| $		1.6	1.2	4.8	2.9
Income tax (expense) benefit \| $		$ (0.7)	$ 0.4	$ (0.1)	$ 1.2
Great Plains Energy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exchange ratio	0.5981
Stock Compensation Plan [Member] \| Great Plains Energy [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares issued \| $	$ 12.5

Short-term Borrowings and Short-term Bank Lines of Credit (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 1,800.0
Line of Credit Facility, Current Borrowing Capacity	2,500.0
Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	675.9
Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	24.1
Master Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,500.0
Long-term Line of Credit	$ 0.0
Credit facility expiration date	Dec. 31, 2023
Evergy [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 449.0	$ 691.8
Line of Credit Facility, Interest Rate at Period End	0.00%	1.83%
Line of Credit Facility, Current Borrowing Capacity	$ 450.0	$ 979.3
Evergy [Member] \| Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit		275.7
Evergy [Member] \| Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	1.0	11.8
Evergy [Member] \| Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100.0
Long-term Line of Credit	$ 0.0	0.0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
Evergy [Member] \| Master Credit Facility [Member] \| Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
KCPL [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 388.1	$ 429.8
Line of Credit Facility, Interest Rate at Period End	2.50%	1.95%
Line of Credit Facility, Current Borrowing Capacity	$ 600.0	$ 600.0
KCPL [Member] \| Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	209.2	167.5
KCPL [Member] \| Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	2.7	2.7
KCPL [Member] \| Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100.0
Long-term Line of Credit	$ 0.0	0.0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
KCPL [Member] \| Master Credit Facility [Member] \| Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Westar Energy Inc [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 655.4	$ 691.8
Line of Credit Facility, Interest Rate at Period End	2.42%	1.83%
Line of Credit Facility, Current Borrowing Capacity	$ 1,000.0	$ 979.3
Westar Energy Inc [Member] \| Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	326.3	275.7
Westar Energy Inc [Member] \| Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	18.3	11.8
Westar Energy Inc [Member] \| Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100.0
Long-term Line of Credit	$ 0.0	0.0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
Westar Energy Inc [Member] \| Master Credit Facility [Member] \| Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Kcpl Greater Missouri Operations Member
Short-term Debt [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 307.5
Line of Credit Facility, Interest Rate at Period End	2.46%
Line of Credit Facility, Current Borrowing Capacity	$ 450.0
Kcpl Greater Missouri Operations Member \| Commercial Paper [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	140.4
Kcpl Greater Missouri Operations Member \| Standby Letters of Credit [Member]
Short-term Debt [Line Items]
Amount of letters of credit outstanding	2.1
Kcpl Greater Missouri Operations Member \| Master Credit Facility [Member]
Short-term Debt [Line Items]
Debt Instrument, Debt Default, Threshold	100.0
Long-term Line of Credit	$ 0.0
Line of Credit Facility, Covenant Terms	A default by any borrower under the facility or one of their significant subsidiaries on other indebtedness totaling more than $100.0 million constitutes a default under the facility. Under the terms of this facility, each of Evergy, Westar Energy, KCP&L and GMO is required to maintain a total indebtedness to total capitalization ratio, as defined in the facility, of not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance	in compliance
Kcpl Greater Missouri Operations Member \| Master Credit Facility [Member] \| Maximum [Member]
Short-term Debt [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Wester Energy Revolving Credit Facility One [Member] \| Westar Energy Inc [Member] \| Master Credit Facility [Member]
Short-term Debt [Line Items]
Line Of Credit, Expired		20.7
Line of Credit Facility, Current Borrowing Capacity		730.0
Wester Energy Revolving Credit Facility Two [Member] \| Westar Energy Inc [Member] \| Master Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity		$ 270.0

Long-Term Debt Long-Term Debt - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Jul. 31, 2018
Debt Instrument [Line Items]
Fair value adjustment		$ 153.0
Long-term debt, including current maturities, of KCP&L, GMO and assumed GPE long-term debt		3,659.7
KCPL [Member] \| Senior Notes [Member] \| Senior Notes Due 2048 KCPL [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 300.0
Interest rates (in hundredths)	4.20%
Maturity date	Dec. 31, 2048
KCPL [Member] \| Senior Notes [Member] \| Senior notes due 2018 KCPL [Member]
Debt Instrument [Line Items]
Interest rates (in hundredths)	6.375%
Repayments of long-term debt	$ 350.0
KCPL [Member] \| Unsecured Debt [Member] \| EIRR bonds 2.875 percent Series 2008 [Member]
Debt Instrument [Line Items]
Debt face amount			$ 23.4
Interest rates (in hundredths)			2.75%
Great Plains Energy [Member] \| Senior Notes [Member] \| Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt face amount		$ 350.0
Interest rates (in hundredths)		4.85%
Great Plains Energy [Member] \| Senior Notes [Member] \| Senior Notes 5.292 Percent Series Due 2022 [Member]
Debt Instrument [Line Items]
Debt face amount		$ 287.5
Interest rates (in hundredths)		5.292%
Kcpl Greater Missouri Operations Member \| Senior Notes [Member] \| Senior Notes Series A due 2025 [Member]
Debt Instrument [Line Items]
Repurchased amount			$ 89.0
Kcpl Greater Missouri Operations Member \| Senior Notes [Member] \| Senior Notes Series B due 2033 [Member]
Debt Instrument [Line Items]
Repurchased amount			$ 15.0

Fair Value Measurements - Debt (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Acquisition, Fair Value Adjustment, Long-Term Debt	$ 153.0
Reported Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Acquisition, Fair Value Adjustment, Long-Term Debt	153.0
Long-term Debt	7,349.4	$ 3,687.6
Reported Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	81.4	109.9
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	7,362.2	4,010.6
Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	80.7	110.8
Westar Energy Inc [Member] \| Reported Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	3,689.7	3,687.6
Westar Energy Inc [Member] \| Reported Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	81.4	109.9
Westar Energy Inc [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	3,750.8	4,010.6
Westar Energy Inc [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Variable Interest Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	80.7	110.8
KCPL [Member] \| Reported Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	2,529.9	2,582.2
KCPL [Member] \| Estimate of Fair Value Measurement [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	$ 2,611.3	$ 2,799.1

Fair Value Measurements - NAV (Details) $ in Millions	9 Months Ended
Fair Value Measurements - NAV (Details) $ in Millions	Sep. 30, 2018 USD ($) fund extension	Dec. 31, 2017 USD ($)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	$ 85.9	$ 37.6
NAV, Unfunded Commitments	4.8	2.8
Westar Energy Inc [Member] \| Decommissioning Trust Assets [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	41.3	37.6
NAV, Unfunded Commitments	4.8	2.8
Westar Energy Inc [Member] \| Alternative Investment Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	23.6	21.7
NAV, Unfunded Commitments	$ 0.0	0.0
NAV, Length of Settlement	65 days
Westar Energy Inc [Member] \| Real Estate Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	$ 11.5	10.8
NAV, Unfunded Commitments	$ 0.0	0.0
NAV, Length of Settlement	65 days
Westar Energy Inc [Member] \| Core Bond Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value		0.0
NAV, Unfunded Commitments	$ 0.0	0.0
Westar Energy Inc [Member] \| Debt Equity Other Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value		0.0
NAV, Unfunded Commitments	0.0	0.0
Westar Energy Inc [Member] \| Rabbi Trusts [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	31.1	0.0
NAV, Unfunded Commitments	0.0	0.0
Other Evergy [Member] \| Rabbi Trusts [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	13.5	0.0
NAV, Unfunded Commitments	0.0	0.0
Geographic Distribution, Domestic [Member] \| Westar Energy Inc [Member] \| Equity Securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Fair Value	6.2	5.1
NAV, Unfunded Commitments	$ 4.8	$ 2.8
NAV, Number of funds \| fund	5
NAV, Number of funds making distributions \| fund	3
Geographic Distribution, Domestic [Member] \| Westar Energy Inc [Member] \| Equity Securities - Fourth Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Length of Settlement	15 years
NAV, Extension term	1 year
NAV, Number of extensions \| extension	3
Geographic Distribution, Domestic [Member] \| Westar Energy Inc [Member] \| Equity Securities - Fifth Fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
NAV, Length of Settlement	15 years

Fair Value Measurements - Gain (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	$ 18.3	$ 24.2	$ 3.4	$ 41.2
Decommissioning Trust Assets - Equity [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	15.1	7.7	1.1	22.2
Rabbi Trusts [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	3.7	16.5	3.1	19.0
Decommissioning Trust Assets - Debt [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	(0.5)	0.0	(0.8)	0.0
Westar Energy Inc [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	10.2	24.2	(3.2)	41.2
Westar Energy Inc [Member] \| Decommissioning Trust Assets - Equity [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	6.5	7.7	(6.4)	22.2
Westar Energy Inc [Member] \| Rabbi Trusts [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	3.7	16.5	3.2	19.0
KCPL [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	8.1	6.9	6.3	18.5
KCPL [Member] \| Decommissioning Trust Assets - Equity [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	8.6	6.9	9.1	17.8
KCPL [Member] \| Decommissioning Trust Assets - Debt [Member]
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Unrealized gain (losses)	$ (0.5)	$ 0.0	$ (2.8)	$ 0.7

Guarantees (Details) $ in Millions	9 Months Ended
Guarantees (Details) $ in Millions	Sep. 30, 2018 USD ($)
Guarantor Obligations [Line Items]
Origin and purpose	In the ordinary course of business, Evergy and certain of its subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries. Such agreements include, for example, guarantees and letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiary's intended business purposes.
Maximum exposure	$ 111.3
Direct Guarantee [Member]
Guarantor Obligations [Line Items]
Origin and purpose	direct guarantees to GMO counterparties
Maximum exposure	$ 17.0
Obligations term	expire in 2020
Guarantee of Indebtedness of Others [Member] \| Long-term Debt [Member]
Guarantor Obligations [Line Items]
Origin and purpose	guarantee of GMO long-term debt
Maximum exposure	$ 94.3
Obligations term	maturity dates ranging from 2019 to 2023
Guarantee of Indebtedness of Others [Member] \| Commercial Paper [Member]
Guarantor Obligations [Line Items]
Origin and purpose	guaranteed GMO's commercial paper program
Maximum exposure	$ 140.4

Related Party Transactions and Relationships (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Westar Energy Inc [Member] \| KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	$ 0.7		$ 0.7		$ 0.0
Westar Energy Inc [Member] \| KCPL [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	(59.3)		(59.3)		0.0
Westar Energy Inc [Member] \| KCPL [Member] \| Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	4.8		10.8
Westar Energy Inc [Member] \| Evergy [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	(14.6)		(14.6)		0.0
Westar Energy Inc [Member] \| Evergy [Member] \| Income Taxes Payable [Member]
Related Party Transaction [Line Items]
Due to related parties	4.4		4.4
KCPL [Member] \| Money Pool [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	0.0		0.0		0.0
KCPL [Member] \| KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	63.3		63.3		65.8
KCPL [Member] \| Westar Energy Inc [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	59.3		59.3		0.0
KCPL [Member] \| Evergy [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	16.4		16.4		0.0
KCPL [Member] \| Evergy [Member] \| Income Taxes Payable [Member]
Related Party Transaction [Line Items]
Due to related parties	21.4		21.4
KCPL [Member] \| Great Plains Energy [Member]
Related Party Transaction [Line Items]
Due from (to) related parties	$ 0.0		$ 0.0		$ 18.9
Iatan No 1 And 2 [Member] \| KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	18.00%		18.00%
Iatan No 1 And 2 [Member] \| KCPL [Member] \| KCPL Greater Missouri Operations [Member] \| Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	$ 43.4	$ 49.2	$ 139.6	$ 145.0
Jeffrey Energy Center [Member] \| KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	8.00%		8.00%
Jeffrey Energy Center [Member] \| Westar Energy Inc [Member] \| KCPL Greater Missouri Operations [Member] \| Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	$ 0.8		$ 4.5
La Cygne Station [Member] \| Westar Energy Inc [Member]
Related Party Transaction [Line Items]
Jointly owned utility plant, proportionate ownership share	50.00%		50.00%
La Cygne Station [Member] \| KCPL [Member] \| Westar Energy Inc [Member] \| Operating Expenses and Capital Costs Billed [Member]
Related Party Transaction [Line Items]
Related party transaction	$ 35.5		$ 50.8

Shareholders' Equity (Details) - USD ($) $ in Millions	9 Months Ended
Shareholders' Equity (Details) - USD ($) $ in Millions	Sep. 30, 2018	Oct. 01, 2018	Aug. 01, 2018	Jul. 31, 2018	Dec. 31, 2017
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	600,000,000				275,000,000
Preferred stock - shares authorized (in shares)	12,000,000
Number of shares authorized to be repurchased (in shares)				60,000,000
Stock Repurchased and Retired During Period, Value	$ 486.1
Stock repurchased and retired during period under repurchase plan, value	$ 486.0
Stock Repurchased and Retired During Period, Shares	6,900,000
Accelerated Share Repurchases, Settlement (Payment) or Receipt			$ (450.0)
Partial Settlement Of Accelerated Share Repurchase Agreement, Shares			6,300,000
Restriction on payment of dividends, minimum ratio of total capitalization	35.00%
Restricted net assets of subsidiaries	$ 5,200.0
Westar Energy Inc [Member]
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	1,000				275,000,000
Restriction on payment of dividends, minimum ratio of total capitalization	40.00%
KCPL [Member]
Common Shareholders' Equity [Line Items]
Common stock - shares authorized (in shares)	1,000				1,000
Restriction on payment of dividends, minimum ratio of total capitalization	40.00%
Retained earnings restrictions	$ 227.4
Subsequent Event [Member]
Common Shareholders' Equity [Line Items]
Additional Shares From Early ASR Settlement		848,226
Maximum [Member] \| Westar Energy Inc [Member] \| Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Maximum [Member] \| KCPL [Member] \| Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Maximum [Member] \| Evergy [Member] \| Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%
Maximum [Member] \| Kcpl Greater Missouri Operations Member \| Master Credit Facility [Member]
Common Shareholders' Equity [Line Items]
Debt Instrument, debt to capitalization ratio	65.00%

Variable Interest Entities (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Property, plant and equipment	$ 18,836.0	$ 9,553.8
Current maturities of long-term debt	709.6	0.0
Accrued interest	119.6	72.7
Long-term debt, net	6,639.8	3,687.6
Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment	170.9	176.3
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.0	0.7
Long-term debt, net	$ 51.1	81.4
Jeffrey Energy Center [Member]
Variable Interest Entity [Line Items]
VIE ownership percentage	8.00%
La Cygne Unit 2 [Member]
Variable Interest Entity [Line Items]
VIE ownership percentage	50.00%
Westar Energy Inc [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment	$ 9,637.5	9,553.8
Current maturities of long-term debt	300.0	0.0
Accrued interest	65.3	72.7
Long-term debt, net	3,389.7	3,687.6
Westar Energy Inc [Member] \| Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment	170.9	176.3
Current maturities of long-term debt	30.3	28.5
Accrued interest	0.0	0.7
Long-term debt, net	$ 51.1	$ 81.4

Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Income Tax Expense (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Current income taxes
Federal	$ (30.3)	$ (16.7)	$ (21.5)	$ (14.5)
State	1.5	0.0	1.9	0.4
Total	(28.8)	(16.7)	(19.6)	(14.1)
Deferred income taxes
Federal	70.6	58.8	86.0	101.7
State	23.3	14.3	(35.7)	27.0
Total	93.9	73.1	50.3	128.7
Investment tax credit amortization	(1.0)	(0.6)	(2.4)	(2.0)
Income tax expense	$ 64.1	$ 55.8	$ 28.3	$ 112.6
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	21.00%	35.00%	21.00%	35.00%
COLI policies	(2.40%)	(4.60%)	(2.40%)	(4.50%)
State income taxes	4.60%	4.30%	4.70%	4.30%
Flow through depreciation for plant-related differences	(1.50%)	2.30%	(1.60%)	2.80%
Federal tax credits	(7.50%)	(7.10%)	(7.50%)	(7.00%)
Non-controlling interest	(0.40%)	(0.50%)	(0.40%)	(0.80%)
AFUDC Equity	(0.10%)	(0.20%)	(0.10%)	(0.20%)
Amortization of federal investment tax credits	(0.60%)	(0.60%)	(0.60%)	(0.60%)
State tax rate change	0.10%	0.00%	(9.50%)	0.00%
Valuation allowance	0.00%	0.00%	0.40%	0.00%
Stock compensation	0.00%	0.00%	(0.50%)	(1.00%)
Officer compensation limitation	1.20%	0.00%	1.20%	0.00%
Other	0.80%	(2.80%)	0.40%	(0.70%)
Effective income tax rate (in hundredths)	15.20%	25.80%	5.10%	27.30%
Westar Energy Inc [Member]
Current income taxes
Federal	$ 8.0	$ (16.7)	$ 18.9	$ (14.5)
State	(9.2)	0.0	(6.7)	0.4
Total	(1.2)	(16.7)	12.2	(14.1)
Deferred income taxes
Federal	12.3	58.8	15.4	101.7
State	12.0	14.3	(47.6)	27.0
Total	24.3	73.1	(32.2)	128.7
Investment tax credit amortization	(0.7)	(0.6)	(2.0)	(2.0)
Income tax expense	$ 22.4	$ 55.8	$ (22.0)	$ 112.6
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	21.00%	35.00%	21.00%	35.00%
COLI policies	(4.00%)	(4.60%)	(4.00%)	(4.50%)
State income taxes	1.10%	4.30%	3.30%	4.30%
Flow through depreciation for plant-related differences	1.50%	2.30%	0.30%	2.80%
Federal tax credits	(11.80%)	(7.10%)	(11.70%)	(7.00%)
Non-controlling interest	(0.60%)	(0.50%)	(0.70%)	(0.80%)
AFUDC Equity	(0.10%)	(0.20%)	(0.10%)	(0.20%)
Amortization of federal investment tax credits	(0.80%)	(0.60%)	(0.80%)	(0.60%)
Changes In Uncertain Tax Positions, Net	0.10%	0.00%	0.10%	0.00%
State tax rate change	0.00%	0.00%	(17.70%)	0.00%
Valuation allowance	0.00%	0.00%	0.60%	0.00%
Stock compensation	0.00%	0.00%	(0.90%)	(1.00%)
Officer compensation limitation	1.90%	0.00%	1.90%	0.00%
Other	2.90%	(2.80%)	1.30%	(0.70%)
Effective income tax rate (in hundredths)	11.20%	25.80%	(7.40%)	27.30%
KCPL [Member]
Current income taxes
Federal	$ 20.7	$ 41.8	$ 43.5	$ 56.2
State	6.8	7.6	11.6	10.2
Total	27.5	49.4	55.1	66.4
Deferred income taxes
Federal	(1.9)	10.3	(23.4)	27.2
State	2.7	2.8	49.4	6.2
Total	0.8	13.1	26.0	33.4
Investment tax credit amortization	(0.3)	(0.3)	(0.8)	(0.8)
Income tax expense	$ 28.0	$ 62.2	$ 80.3	$ 99.0
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	21.00%	35.00%	21.00%	35.00%
COLI policies	(0.20%)	(0.30%)	(0.20%)	(0.30%)
State income taxes	5.00%	3.90%	5.10%	3.90%
Flow through depreciation for plant-related differences	(4.90%)	0.10%	(4.90%)	0.20%
Federal tax credits	(1.90%)	(3.10%)	(1.80%)	(2.60%)
AFUDC Equity	0.00%	(0.70%)	(0.10%)	(0.70%)
Amortization of federal investment tax credits	(0.40%)	(0.40%)	(0.40%)	(0.40%)
State tax rate change	0.00%	0.00%	14.50%	0.00%
Valuation allowance	0.00%	0.60%	0.00%	0.40%
Stock compensation	0.00%	0.10%	0.00%	0.20%
Officer compensation limitation	0.70%	0.00%	0.50%	0.00%
Other	(0.40%)	0.10%	(1.00%)	0.10%
Effective income tax rate (in hundredths)	18.90%	35.30%	32.70%	35.80%

Taxes Tax Reform (Details) - USD ($) $ in Millions	Jun. 01, 2018	Sep. 30, 2018	Dec. 31, 2017
Regulatory liabilities		$ 2,357.1	$ 1,094.0
Revenue Subject to Refund [Member]
Regulatory liabilities		155.1
Westar Energy Inc [Member]
Regulatory liabilities		1,136.9	1,094.0
Westar Energy Inc [Member] \| Revenue Subject to Refund [Member]
Regulatory liabilities		66.3
KCPL [Member]
Regulatory liabilities		862.9	$ 770.9
Decrease in net deferred income tax liabilities due to tax reform	$ 46.6
Decrease in net deferred income tax liabilities for revaluation of deferred income tax assets and liabilities in rate base	28.8
Decrease in net deferred income tax liabilities for tax gross-up adjustment for ratemaking purposes due to tax reform	9.9
Income tax benefit from tax reform	$ 15.5
KCPL [Member] \| Revenue Subject to Refund [Member]
Regulatory liabilities		$ 64.6