Supplemental Cash Flow Elements [Abstract] Cash Flow, Supplemental Disclosures [Text Block] Cash Flow, Supplemental Disclosures [Text Block] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Kansas City Power and Light Company [Member] Subsidiaries [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Series B Preferred Stock [Member] Series B Preferred Stock [Member] Cumulative Preferred Stock [Member] Cumulative Preferred Stock [Member] No Par Preference Stock [Member] No Par Preference Stock [Member] Preference stock, with no stated par value, authorized under the Articles of Incorporation. Statement [Line Items] Statement [Line Items] ASSETS Assets [Abstract] Utility Plant, at Original Cost Public Utilities, Property, Plant and Equipment, Net [Abstract] Nuclear fuel, amortization Nuclear Fuel Accumulated Amortization Amortization based on the energy produced over the life of the fuel. LIABILITIES AND CAPITALIZATION Liabilities and Equity [Abstract] Capitalization Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Shareholder's equity Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Common stock - shares authorized (in shares) Common Stock, Shares Authorized Common stock-shares issued (in shares) Common Stock, Shares, Issued Preferred Stock, Shares Issued Preferred Stock, Shares Issued Preferred Stock, Dividend Rate, Percentage Preferred Stock, Dividend Rate, Percentage Preferred Stock, Liquidation Preference Per Share Preferred Stock, Liquidation Preference Per Share Preference stock, Shares Authorized Preferred Stock, Shares Authorized Treasury stock- shares (in shares) Treasury Stock, Shares Cumulative preferred stock par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Net Operating Loss Carryforwards Disclosure [Abstract] Net Operating Loss Carryforwards Disclosure [Abstract] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Internal Revenue Service (IRS) [Member] Internal Revenue Service (IRS) [Member] State and Local Jurisdiction [Member] State and Local Jurisdiction [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Tax Credit Carryforward, Amount Tax Credit Carryforward, Amount Operating Loss Carryforwards Operating Loss Carryforwards Amount of Net Operating Losses related to business acquisition Amount of Net Operating Losses related to business acquisition The amount of net operating loss carryforwards acquired in in the GMO acquisition. Operating Loss Carryforwards, Valuation Allowance Operating Loss Carryforwards, Valuation Allowance Operating Loss Carryforwards, Expiration Date Operating Loss Carryforwards, Expiration Date Net operating losses year of origination [Abstract] Net operating losses year of origination [Abstract] Net operating losses year of origination [Abstract] Net operating loss carryforwards originating in 2003 Net operating loss carryforwards originating in 2003 Net operating loss carryfowards originating in 2003 Net operating loss carryfowards originating in 2004 Net operating loss carryfowards originating in 2004 Net operating loss carryfowards originating in 2004 Net operating loss carryfowards originating in 2005 Net operating loss carryfowards originating in 2005 Net operating loss carryfowards originating in 2005 Net operating loss carryfowards originating in 2006 Net operating loss carryfowards originating in 2006 Net operating loss carryfowards originating in 2006 Net operating loss carryfowards originating in 2007 Net operating loss carryfowards originating in 2007 Net operating loss carryfowards originating in 2007 Net operating loss carryfowards originating in 2008 Net operating loss carryfowards originating in 2008 Net operating loss carryfowards originating in 2008 Net operating loss carryfowards originating in 2009 Net operating loss carryfowards originating in 2009 Net operating loss carryfowards originating in 2009 Net operating loss carryfowards originating in 2010 Net operating loss carryfowards originating in 2010 Net operating loss carryfowards originating in 2010 Net operating loss carryfowards originating in 2011 Net operating loss carryfowards originating in 2011 Net operating loss carryfowards originating in 2011 Net operating loss carryforwards originating in 2012 Net Operating Loss Carryforwards Originating In 2012 Net operating loss carryforwards originating in 2012 Net operating loss carryforwards originating in 2013 Net Operating Loss Carryforwards Originating In 2013 Net operating loss carryforwards originating in 2013. Net operating loss carryforwards originating in 2014 Net Operating Loss Carryforwards Originating In 2014 Net operating loss carryforwards originating in 2014 Net operating loss carryforwards originating in 2015 Net Operating Loss Carry Forwards Originating In 2015 Net Operating Loss Carry Forwards Originating in 2015 Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments [Member] Other [Member] Corporate, Non-Segment [Member] Eliminations [Member] Intersegment Eliminations [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Electric Utility Segment [Member] Electric Utility Segment [Member] Electric Utility Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Operating revenues Electric Revenue Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Interest charges Interest Expense Income tax (expense) benefit Income Tax Expense (Benefit) Net income (loss) Net Income (Loss) Attributable to Parent Assets Assets Capital expenditures Payments to Acquire Property, Plant, and Equipment Legal Proceedings [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingencies by Nature of Contingency [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Unfavorable Regulatory Action [Member] Unfavorable Regulatory Action [Member] MPS Merchant Services, Inc. [Member] MPS Merchant Services, Inc [Member] MPS Merchant Services, Inc. [Member] KCPL Greater Missouri Operations [Member] Kcpl Greater Missouri Operations Member Information on KCPL Greater Missouri Operations. Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] GMO Western Energy Crisis [Member] GMO Western Energy Crisis [Member] GMO Western Energy Crisis Loss Contingencies [Line Items] Loss Contingencies [Line Items] Litigation Settlement, Amount Estimated additional refunds entitled to receive Estimated Additional Refunds Entitled To Receive Estimated additional refunds entitled to receive. Loss recorded in other operating expenses Other Cost and Expense, Operating Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative [Table] Derivative [Table] Derivative, by Nature [Axis] Derivative Instrument [Axis] Derivative, Name [Domain] Derivative Contract [Domain] Futures contracts [Member] Future [Member] Forward Contracts [Member] Forward Contracts [Member] Option contracts [Member] Options Held [Member] Transmission Congestion Rights [Member] Transmission Congestion Rights [Member] Financial contracts acquired as part of the Southwest Power Pool's Integrated Marketplace that can be used to hedge against congestion costs and protect load prices. Interest Rate Swap [Member] Interest Rate Swap [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Not Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument [Member] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash Flow Hedging [Member] Cash Flow Hedging [Member] Derivative [Line Items] Derivative [Line Items] Price Risk Derivatives [Abstract] Price Risk Derivatives [Abstract] Percentage of projected natural gas usage hedged year one Percentage Of Projected Natural Gas Usage Hedged Year One Percentage of projected natural gas usage hedged for the year following the balance sheet date. Percentage of projected natural gas usage hedged year two Percentage Of Projected Natural Gas Usage Hedged Year Two Percentage of projected natural gas usage hedged for the second year following the balance sheet date. Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged remainder of fiscal year Percentage Of Expected On Peak Natural Gas And Natural Gas Equivalent Purchased Power Price Exposure Hedged Remainder Of Fiscal Year Percentage of expected on-peak natural gas and natural gas equivalent purchased power price exposure that is hedged for the remainder of the current fiscal year. Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged year one Percentage Of Expected On Peak Natural Gas And Natural Gas Equivalent Purchased Power Price Exposure Hedged Year One Percentage of expected on-peak natural gas and natural gas equivalent purchased power price exposure that is hedged for the year following the balance sheet date. Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged year two Percentage Of Expected On Peak Natural Gas And Natural Gas Equivalent Purchased Power Price Exposure Hedged Year Two Percentage of expected on-peak natural gas and natural gas equivalent purchased power price exposure that is hedged for the second year following the balance sheet date. Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged year three Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged year three Percentage of projected natural gas usage hedged for the third year following the balance sheet date. Percentage Of Expected On Peak Natural Gas And Natural Gas Equivalent Purchased Power Price Exposure Hedged Percentage Of Expected On Peak Natural Gas And Natural Gas Equivalent Purchased Power Price Exposure Hedged Percentage of expected on-peak natural gas and natural gas equivalent purchased power price exposure that is hedged at end of period Percentage Of Expected Natural Gas Equivalent Bulk Power Sales Price Exposure Hedged Percentage Of Expected Natural Gas Equivalent Bulk Power Sales Price Exposure Hedged Remainder Of Fiscal Year Percentage of expected natural gas equivalent bulk power sales price exposure that is hedged for the remainder of the current fiscal year. Percentage Of Expected Summer Month Natural Gas Generation For Missouri Jurisdictional Retail Sales Hedged Remainder Of Fiscal Year Percentage Of Expected Summer Month Natural Gas Generation For Missouri Jurisdictional Retail Sales Hedged Remainder Of Fiscal Year Percentage of the expected summer month natural gas generation for Missouri jurisdictional retail sales hedged remainder of fiscal year Percentage Of Expected Summer Month Natural Gas Generation For Missouri Jurisdictional Retail Sales Hedged Year Two Percentage Of Expected Summer Month Natural Gas Generation For Missouri Jurisdictional Retail Sales Hedged Year Two Percentage of expected summer month natural gas generation for Missouri jurisdictional retail sales hedged for the second year following the balance sheet date. Percentage Of Expected Summer Month Natural Gas Generation For Missouri Jurisdictional Retail Sales Hedged Year Three Percentage Of Expected Summer Month Natural Gas Generation For Missouri Jurisdictional Retail Sales Hedged Year Three Percentage of expected summer month natural gas generation for Missouri jurisdictional retail sales hedged for the third year following balance sheet date. Notional Contract Amount Derivative, Notional Amount Fair Value Derivative, Fair Value, Net Short-term Borrowings and Short-term Bank Lines of Credit [Abstract] Short-term Borrowings and Short-term Bank Lines of Credit [Text Block] Short-term Debt [Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Domain] Jointly Owned Utility Plant [Domain] Iatan No 1 And 2 [Member] Jointly Owned Electricity Generation Plant Iatan No 1 And 2 [Member] Jointly Owned Electricity Generation Plant Iatan No 1 And 2 [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Great Plains Energy [Member] Great Plains Energy [Member] Information on Great Plains Energy. Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Operating Expenses and Capital Costs Billed [Member] Operating Expenses And Capital Costs Billed [Member] Operating Expenses and Capital Costs Billed [Member] Money Pool [Member] Money Pool [Member] Transactions related to the Great Plains Energy Money Pool, an internal financing arrangement between Great Plains Energy, KCP&L and GMO. Related Party Transaction [Line Items] Related Party Transaction [Line Items] Receivable from Related Party Due from Related Parties, Current Related Party Transaction, Due from (to) Related Party, Current Related Party Transaction, Due from (to) Related Party, Current Operating expenses and capital costs billed from KCPL to GMO Related Party Transaction, Amounts of Transaction KCPL net wholesale sales to GMO Related Party Transaction, Other Revenues from Transactions with Related Party Jointly Owned Utility Plant, Proportionate Ownership Share Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Derivative Instrument [Axis] Derivative Contract [Domain] Interest Rate Contract [Member] Interest Rate Contract [Member] Commodity Contract [Member] Commodity Contract [Member] Income tax benefit (expense) [Member] Income tax benefit (expense) [Member] Benefit (expense) from income taxes due to gain (loss) recognized. Regulatory Account [Member] Regulatory Account [Member] Derivative instruments in a regulatory account relationship. Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Interest Charges [Member] Interest Expense [Member] Fuel Costs [Member] Fuel Costs [Member] Fuel costs incurred that are directly related to goods produced and sold and services rendered during the reporting period. Purchased Power Costs [Member] Purchased Power Costs [Member] Amount of operating expense for purchased power of regulated operation. Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Amount of Gain (Loss) Recognized in OCI on Derivatives (Effective Portion) Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net Gain(Loss) Reclassified from Regulatory Account into Income Derivative Instruments Gain Loss Reclassified From Regulatory Account Into Income On Derivatives The income statement location of the net gain (loss) reclassified from a regulatory account into income on derivative instruments. Tax Credit Carryforward Disclosure [Abstract] Tax Credit Carryforward Disclosure [Abstract] Tax Credit Carryforward [Table] Tax Credit Carryforward [Table] Tax Credit Carryforward [Axis] Tax Credit Carryforward [Axis] Tax Credit Carryforward, Name [Domain] Tax Credit Carryforward, Name [Domain] General Business Tax Credit Carryforward [Member] General Business Tax Credit Carryforward [Member] Federal Alternative Minimum Tax Credit Carryforward [Member] Federal Alternative Minimum Tax Credit Carryforward [Member] Tax credit carryforwards related to the federal Alternative Minimum Tax Tax Credit Carryforward [Line Items] Tax Credit Carryforward [Line Items] Amount of tax credit acquired in business combination Amount of tax credit acquired in business combination Amount of tax credit acquired in GMO acquisition Tax Credit Carryforward, Description Tax Credit Carryforward, Description Tax Credit Carryforward, Expiration Date Tax Credit Carryforward, Expiration Date Tax Credit Carryforward, Valuation Allowance Tax Credit Carryforward, Valuation Allowance Valuation Allowance, Deferred Tax Asset, Explanation of Change Valuation Allowance, Deferred Tax Asset, Explanation of Change Receivables [Abstract] Schedule of receivables [Table Text Block] Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Quarterly Financial Information Disclosure [Abstract] Schedule of Quarterly Financial Information [Table Text Block] Quarterly Financial Information [Table Text Block] Guarantees [Abstract] Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Direct Guarantee [Member] Financial Guarantee [Member] Standby Letters of Credit [Member] Standby Letters of Credit [Member] Guarantee of Indebtedness of Others [Member] Guarantee of Indebtedness of Others [Member] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Commercial Paper [Member] Commercial Paper [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Long-term Debt [Member] Long-term Debt [Member] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Guarantor Obligations, Term Guarantor Obligations, Term Guarantor Obligations, Origin and Purpose Guarantor Obligations, Origin and Purpose Guarantor Obligations, Maximum Exposure Inestimable Guarantor Obligations, Maximum Exposure Inestimable Accounting Policies [Abstract] Schedule of Public Utility Property, Plant, and Equipment [Table Text Block] Public Utility Property, Plant, and Equipment [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] New Accounting Pronouncement, Early Adoption [Table Text Block] New Accounting Pronouncement, Early Adoption [Table Text Block] Sale Of Accounts Receivable - KCPL and GMO Sale Of Accounts Receivable - KCPL and GMO [Line Items] [Abstract] Sale Of Accounts Receivable - KCPL and GMO [Line Items] [Abstract] Accounts receivable pledged as collateral Transfers Accounted for as Secured Borrowings, Assets, Carrying Amount Collateralized note payable Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount Maximum amount of outstanding principal under receivables agreement from mid-November to mid-June MaximumAmountOfOutstandingPrincipalUnderReceivablesAgreementFromMidNovToMidJun MaximumAmountOfOutstandingPrincipalUnderReceivablesAgreementFromMidNovToMidJun Maximum amount of outstanding principal under receivables agreement Maximum Amount Of Outstanding Principal Under Receivables Agreement Maximum amount of outstanding principal under receivables agreement Maximum amount of outstanding principal under receivables agreement from mid-June to mid-November MaximumAmountOfOutstandingPrincipalUnderReceivablesAgreementFromMidJunToMidNov MaximumAmountOfOutstandingPrincipalUnderReceivablesAgreementFromMidJunToMidNov Regulated Operations [Abstract] Schedule Of Regulatory Assets And Liabilities [Table Text Block] Schedule Of Regulatory Assets And Liabilities [Table Text Block] Tabular disclosure of assets and liabilities created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet or when the rate actions of a regulator impose a liability on a regulated enterprise resulting in a regulatory liability. Organization [Policy Text Block] Consolidation, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Use of Estimates, Policy [Policy Text Block] Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents, Policy [Policy Text Block] Time Deposit, Policy [Policy Text Block] TimeDepositPolicyTextBlock [Policy Text Block] Time Deposit Policy [Policy Text Block] Funds on Deposit, Policy [Policy Text Block] Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Fair Value of Financial Instruments, Policy [Policy Text Block] Fair Value of Financial Instruments, Policy [Policy Text Block] Derivatives, Policy [Policy Text Block] Derivatives, Policy [Policy Text Block] Utility Plant, Policy [Policy Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Depreciation and Amortization, Policy [Policy Text Block] Regulatory Depreciation and Amortization, Policy [Policy Text Block] Nuclear Plant Decommissioning Costs, Policy [Policy Text Block] Asset Retirement Obligations, Policy [Policy Text Block] Deferred Refueling Outage Costs, Policy [Policy Text Block] Property, Plant and Equipment, Planned Major Maintenance Activities, Policy [Policy Text Block] Regulatory Matters, Policy [Policy Text Block] Public Utilities, Policy [Policy Text Block] Revenue Recognition, Policy [Policy Text Block] Revenue Recognition, Policy [Policy Text Block] Allowance for Doubtful Accounts, Policy [Policy Text Block] Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Property Gains And Losses, Policy [Policy Text Block] Property Gains And Losses [Policy Text Block] Disclosure of accounting policy for gains and losses on sales of property and from asset impairments. Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Asset Impairments, Policy [Policy Text Block] Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy [Policy Text Block] Income Taxes, Policy [Policy Text Block] Income Tax, Policy [Policy Text Block] Environmental Matters, Policy [Policy Text Block] Regulatory Environmental Costs, Policy [Policy Text Block] Basic and Diluted Earnings per Common Share Calculation [Policy Text Block] Earnings Per Share, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements, Policy [Policy Text Block] Schedule of related party receivables and payables [Table Text Block] Schedule of related party receivables and payables [Table Text Block] Tabular disclosure of related party receivables and payables. Commitments and Contingencies Disclosure [Abstract] Estimates Of Environmental Financial Impact And Related Issues [Table] Estimates Of Environmental Financial Impact And Related Issues [Table] Supply Commitment [Axis] Supply Commitment [Axis] Supply Commitment Arrangement [Domain] Supply Commitment Arrangement [Domain] Supply Commitment [Member] Supply Commitment [Member] Westar Energy Inc [Member] Westar Energy Inc [Member] Utility operating in Kansas. Jeffrey Units Nos 1 and 2 [Member] JointlyOwnedElectricityGenerationsPlantJeffrey Units Nos 1 and 2 [Member] Jeffrey Units Number 1 and 2, a jointly owned plant in connection with generation of electricity, excluding nuclear. LaCygne Station [Member] JointlyOwnedElectricityGenerationPlantLaCygneStation [Member] LaCygne Station, a jointly owned plant in connection with generation of electricity, excluding nuclear. Iatan No. 1 [Member] Jointly Owned Electricity Generation Plant Iatan No 1 [Member] Information on the jointly owned Iatan No. 1 electric utility plant. Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] MISSOURI MISSOURI KANSAS KANSAS Estimates Of Environmental Financial Impact And Related Issues [Line Items] Estimates Of Environmental Financial Impact And Related Issues [Line Items] Estimated Environmental Capital Expenditures [Abstract] Estimated Environmental Capital Expenditures [Abstract] Estimated Environmental Capital Expenditures [Abstract] Estimate Of Environmental Capital Expenditures Current Estimate Of Environmental Capital Expenditures Current Current estimate of capital expenditures (exclusive of Allowance for Funds Used During Construction and property taxes) to comply with environmental regulations in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Estimate Of Environmental Capital Expenditures In Two Years Estimate Of Environmental Capital Expenditures In Two Years Current estimate of capital expenditures (exclusive of Allowance for Funds Used During Construction and property taxes) to comply with environmental regulations in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Estimate Of Environmental Capital Expenditures In Three Years Estimate Of Environmental Capital Expenditures In Three Years Current estimate of capital expenditures (exclusive of Allowance for Funds Used During Construction and property taxes) to comply with environmental regulations in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Estimate Of Environmental Capital Expenditures In Four Years Estimate Of Environmental Capital Expenditures In Four Years Current estimate of capital expenditures (exclusive of Allowance for Funds Used During Construction and property taxes) to comply with environmental regulations in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Estimate Of Environmental Capital Expenditures In Five Years Estimate Of Environmental Capital Expenditures In Five Years Current estimate of capital expenditures (exclusive of Allowance for Funds Used During Construction and property taxes) to comply with environmental regulations in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Clean Air Act and Climate Change [Abstract] Clean Air Act and Climate Change [Abstract] -- None. No documentation exists for this element. -- Mercury and Air Toxics Standards Rule [Abstract] Mercury and Air Toxics Standards Rule [Abstract] -- None. No documentation exists for this element. -- Capacity of electric steam generating units that fall under MACT standards (in megawatts) Capacity of electric steam generating units that fall under MACT standards in mw New MACT rules will apply to all new or existing coal-fired electric generating units with a capacity equal to or greater than this amount. SO2 National Ambient Air Quality Standard (NAAQS) [Abstract] So2 National Ambient Air Quality Standard [Abstract] Primary one-hour sulfur dioxide standard, as revised June 2010 (in parts per million) Revised Parts Per Million For Sulphur Dioxide Established For Primary Standard Represents the primary one-hour sulfur dioxide standard as revised by the Environmental Protection Agency in June 2010 to replace the exisiting 24-hour and one-year standards. Primary twenty-four hour sulfur dioxide standard, prior to June 2010 (in parts per million) Revoked Parts Per Million For Sulphur Dioxide For Primary Standard Over1 Day Represents the primary twenty-four hour sulfur dioxide standard revoked by the Environmental Protection Agency in June 2010. Primary one-year sulfur dioxide standard, prior to June 2010 (in parts per million) Revoked Parts Per Million For Sulphur Dioxide For Primary Standard Over1 Year Represents the primary one-year sulfur dioxide standard revoked by the Environmental Protection Agency in June 2010. Climate Change [Abstract] Climate Change [Abstract] CO2 produced per year (in millions of tons) Estimated Number Of Tons Of Co2 Produced Per Year Represents the estimated number of tons of CO2 produced each year based on current generation capacity. EPA nationwide CO2 emission reductions by 2030 EPA Co2 Emission Reductions By 2030 Nationwide Targeted nationwide reductions in CO2 emissions from the power sector by 2030 from 2005 emission levels as part of the EPA's Clean Power Plan. EPA Interim Co2 Goal Rate Reduction EPA Interim Co2 Goal Rate Reduction The interim CO2 goal rate reduction (average of years 2022-2029) from 2012 CO2 emissions as adjusted by the EPA as part of the EPA's Clean Power Plan. EPA Co2 Emission Reductions By 2030 By State EPA Co2 Emission Reductions By 2030 By State Targeted reduction by state in CO2 emissions from the power sector by 2030 from 2012 emission levels as adjusted by the EPA as part of the EPA's Clean Power Plan. Remediation [Abstract] Environmental Remediation Obligations [Abstract] Accrued environmental remediation expenses Accrued Environmental Loss Contingencies, Noncurrent Estimated amount of insurance proceeds available to cover qualified remediation expenses Estimated Dollar Amount Of Available Insurance Proceeds To Cover Qualified Remediation Expense Represents the estimated amount of insurance proceeds available, less an annual deductible, to GMO cover qualified MGP remediation expenses. Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Tax Disclosure [Text Block] Statement of Cash Flows [Abstract] Great Plains Energy [Member] Parent Company [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Cash Flows from Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Adjustments to reconcile income to net cash from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Amortization Amortization Deferred income taxes, net Deferred Income Tax Expense (Benefit) Equity in earnings from subsidiaries Income (Loss) from Equity Method Investments Fair value impact of interest rate swaps Unrealized Gain (Loss) on Derivatives and Commodity Contracts Cash flows affected by changes in: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable from subsidiaries Increase (Decrease) in Due from Related Parties Taxes receivable Increase (Decrease) in Income Taxes Receivable Accounts payable to subsidiaries Increase (Decrease) in Due to Related Parties Other accounts payable Increase (Decrease) in Other Accounts Payable and Accrued Liabilities Accrued taxes Increase (Decrease) in Accrued Taxes Payable Accrued interest Increase (Decrease) in Interest Payable, Net Cash dividends from subsidiaries Cash Dividends Paid to Parent Company by Consolidated Subsidiaries Uncertain tax positions Increase Decrease In Uncertain Tax Positions The increase (decrease) during the reporting period in the value of uncertain tax positions. Other Other Operating Activities, Cash Flow Statement Net cash from operating activities Net Cash Provided by (Used in) Operating Activities Cash Flows from Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Purchase of time deposit Payment To Invest In Time Deposit The cash outflow for the purchase of a time deposit. Intercompany lending Intercompany lending Cash outflows (inflows) from intercompany lending. Net money pool lending Net money pool lending The net cash outflows or inflows in money pool lending. Investment in subsidiary Payments to Acquire Interest in Subsidiaries and Affiliates Other investing activities Payments for (Proceeds from) Other Investing Activities Net cash from investing activities Net Cash Provided by (Used in) Investing Activities Cash Flows from Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Issuance of common stock Proceeds from Issuance of Common Stock Issuance of preference stock Proceeds from Issuance of Preferred Stock and Preference Stock Issuance of long-term debt Proceeds from Issuance of Long-term Debt Issuance fees Payment of Financing and Stock Issuance Costs Repayment of long-term debt Repayments of Long-term Debt Net change in short-term borrowings Proceeds from (Repayments of) Short-term Debt Dividends paid Payments of Dividends Redemption of cumulative preferred stock Payments for Repurchase of Preferred Stock and Preference Stock Purchase of treasury stock Payments for Repurchase of Common Stock Other financing activities Proceeds from (Payments for) Other Financing Activities Net cash from financing activities Net Cash Provided by (Used in) Financing Activities Net Change in Cash and Cash Equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and Cash Equivalents at Beginning of Year Cash and Cash Equivalents, at Carrying Value Cash and Cash Equivalents at End of Year Compensation and Retirement Disclosure [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Wolf Creek [Member] Jointly Owned Nuclear Power Plant [Member] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plans, Defined Benefit [Member] Pension Plan [Member] Other Postretirement Benefit Plans, Defined Benefit [Member] Other Postretirement Benefit Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Jointly Owned Utility Plant, Proportionate Ownership Share Defined Benefit Plan, Contributions by Employer Defined Benefit Plan, Contributions by Employer Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Defined Benefit Plan, Benefit Obligation Defined Benefit Plan, Benefit Obligation Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Contributions by participants Defined Benefit Plan, Contributions by Plan Participants Amendments Defined Benefit Plan, Plan Amendments Actuarial (gain) loss Defined Benefit Plan, Actuarial Gain (Loss) Benefits Paid Defined Benefit Plan, Benefits Paid Defined Benefit Plan, Settlements, Benefit Obligation Defined Benefit Plan, Settlements, Benefit Obligation Defined Benefit Plan, Benefit Obligation Change in plan assets [Roll Forward] Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Fair value of plan assets at beginning of the year Defined Benefit Plan, Fair Value of Plan Assets Actual return on plan assets Defined Benefit Plan, Actual Return on Plan Assets Contributions by employer and participants Defined Benefit Plan Contributions by Employer and Participants The increase in the fair value of plan assets from contributions made by the employer and plan participants. Benefits paid Defined Benefit Plan Benefits Paid Portion Paid from Plan Assets The amount of payments paid from plan assets for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets. Defined Benefit Plan, Settlements, Plan Assets Defined Benefit Plan, Settlements, Plan Assets Fair value of plan assets at end of the year Funded status at end of year Defined Benefit Plan, Funded Status of Plan Amounts recognized in the consolidated balance sheets [Abstract] Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract] Non-current asset Defined Benefit Plan, Assets for Plan Benefits, Noncurrent Current pension and other post-retirement liability Pension and Other Postretirement Defined Benefit Plans, Current Liabilities Noncurrent pension liability and other post-retirement liability Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Net amount recognized before regulatory treatment Defined Benefit Plan Amounts Recognized in Balance Sheet before Regulatory Treatment The aggregate net amount recognized in the balance sheet associated with the defined benefit plan(s) before OCI/regulatory treatment. Defined benefit plan amount recognized in Accumulated Other Comprehensive Income or Regulatory Asset Liability The aggregate amount recognized in accumulated other comprehensive income, regulatory assets and regulatory liabilities associated with the defined benefit plan(s). Defined Benefit Plan, Amounts Recognized in Balance Sheet Defined Benefit Plan, Amounts Recognized in Balance Sheet Amounts in accumulated other comprehensive income or regulatory asset/liability not yet recognized as a component of net periodic benefit cost [Abstract] Amounts in accumulated other comprehensive income or regulatory asset liability not yet recognized as a component of net periodic benefit cost [Abstract] -- None. No documentation exists for this element. -- Actuarial (gain) loss Defined Benefit Plan Accumulated Other Comprehensive Income Or Regulatory Asset Liability Net Gains Losses Before Tax The pretax net amount of gains and losses that are not yet recognized as a component of net periodic benefit cost, and that are recognized as increases or decreases in other comprehensive income or regulatory (assets) liabilities as they arise. Gains and losses are due to changes in the value of either the benefit obligation or the plan assets. Prior service cost Defined Benefit Plan Accumulated Other Comprehensive Income Or Regulatory Asset Liability Net Prior Service Cost Credit Before Tax Amount related to the pretax cost of benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation, which has not yet been recognized as components of net periodic benefit cost. Defined Benefit Plan Accumulated Other Comprehensive Income Or Regulatory Asset/Liability Net Transition Obligation Before Tax Defined Benefit Plan Accumulated Other Comprehensive Income Or Regulatory Asset Liability Net Transition Obligation Before Tax Of the original amount of transition assets as of the date FAS 87 or 106 was initially applied, the portion of which has yet to be recognized as components of net periodic benefit cost. This amount is pretax. Other Defined Benefit Plan Accumulated Other Comprehensive Income Or Regulatory Asset Liability Other Before Tax Amount related to other amounts recorded in accumulated other comprehensive income or regulatory (assets) liabilities, before tax. Components of net periodic benefit costs [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] Expected return on plan assets Defined Benefit Plan, Expected Return on Plan Assets Prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Recognized net actuarial (gain)/loss Defined Benefit Plan, Amortization of Gains (Losses) Transition obligation Defined Benefit Plan, Amortization of Transition Obligations (Assets) Settlement charges Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements Net periodic benefit costs before regulatory adjustment Net period benefit costs before regulatory adjustment The total amount of net periodic benefit cost for defined benefit plans for the period before regulatory adjustment. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments. Regulatory adjustment Defined Benefit Plan Regulatory Adjustment Increase (decrease) in net periodic benefit costs related to regulatory adjustments. Net periodic benefit costs Defined Benefit Plan, Net Periodic Benefit Cost Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets/Liabilities [Abstract] Other Changes In Plan Assets And Benefit Obligations Recognized In Other Comprehensive Income Regulatory Assets Liabilities [Abstract] -- None. No documentation exists for this element. -- Current year net (gain) loss Other Comprehensive Income (Loss) Or Regulatory Asset Liability, Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax Amount before tax of (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit. Amortization of gain (loss) Other Comprehensive Income (Loss) Or Regulatory Asset Liability, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax Amount before tax of reclassification adjustment from accumulated other comprehensive income (loss) or regulatory asset/liability related to pension and other postretirement benefit plans. Prior service cost Other Comprehensive (Income) Loss or Regulatory Asset Liability, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax Amount before tax of cost (credit) of benefit changes attributable to plan participants' prior service resulting from a plan amendment or plan initiation that has not been recognized in net periodic benefit costs (credit). Amortization of prior service cost Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI or Regulatory Asset Liability, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax Amount before tax of reclassification adjustment from accumulated other comprehensive (income) loss or regulatory asset/liability for prior service cost (credit) related to pension and other postretirement benefit plans. Amortization of transition obligation Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI or Regulatory AssetLiability, Pension and Other Postretirement Benefit Plans, for Net Transition Asset (Obligation), before Tax Amount before tax of reclassification adjustment from accumulated other comprehensive income (loss) or regulatory asset/liability for net transition asset (obligation) related to pension and other postretirement benefit plans. Other regulatory activity OtherComprehensiveIncomeLossOrRegulatoryAssetLiabilityPensionAndOtherPostretirementBenefitPlansOtherRegulatoryActivity Changes in pension and postretirement benefit plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities due to other regulatory activity. Total Recognized In Other Comprehensive Income Or Regulatory Asset/Liability Total Recognized In Other Comprehensive Income Or Regulatory Asset Liability The total recognized in other comprehensive income or regulatory assets/liabilities. Total Recognized In Net Periodic Benefit Costs And Other Comprehensive Income Or Regulatory Asset/Liability Total Recognized In Net Periodic Benefit Costs And Other Comprehensive Income Or Regulatory Asset Liability Total recognized in net periodic benefit costs and other comprehensive income or regulatory asset/liability. Estimated prior service cost that will be amortized in the next fiscal year Defined Benefit Plan, Future Amortization of Prior Service Cost From AOCI Or Regulatory Asset Amount included in accumulated other comprehensive income (AOCI) or a regulatory asset related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position. Net (gain) loss for the defined benefit plans that will be amortized in the next fiscal year Defined Benefit Plan, Future Amortization of Gain (Loss) From AOCI Or Regulatory Asset Amount included in accumulated other comprehensive income (AOCI) or a regulatory asset related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position. Transition costs for the defined benefit plans that will be amortized in the next fiscal year Defined Benefit Plan, Future Amortization of Transition Obligation (Asset) From AOCI Or Regulatory Asset Amount included in accumulated other comprehensive income (AOCI) or a regulatory asset related to transition obligation (asset) expected to be recognized as components of net periodic benefit cost (credit) for the fiscal year that follows the most recent annual statement of financial position. Length Of Time For Amortization Of Net Actuarial Gains And Losses For Financial Reporting Purposes Length Of Time For Amortization Of Net Actuarial Gains And Losses For Financial Reporting Purposes The length of time for amortization of net actuarial gains and losses for financial reporting purposes. Length Of Time For Amortization Of Net Actuarial Gains And Losses For Regulatory Reporting Purposes Length Of Time For Amortization Of Net Actuarial Gains And Losses For Regulatory Reporting Purposes The length of time for amortization of net actuarial gains and losses for regulatory reporting purposes. Accumulated benefit obligation (ABO) for all defined benefit plans Defined Benefit Plan, Accumulated Benefit Obligation Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract] Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract] Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Benefit Obligation Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Benefit Obligation Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets Pension plans with the accumulated benefit obligation in excess of plans assets [Abstract] Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract] Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets Unfunded accumulated benefit obligation for GMO SERP Unfunded accumulated benefit obligation for GMO SERP The unfunded accumulated benefit obligation related to the GMO SERP acquired in the GMO acquisition. Segregated assets for GMO SERP Segregated assets for GMO SERP Assets that have been segregated to cover the unfunded GMO SERP acquired in the GMO acquisition. Weighted average assumptions used to determine the benefit obligation [Abstract] Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Defined Benefit Plan, Assumptions Used in Calculations, Narrative Description Defined Benefit Plan, Assumptions Used in Calculations, Narrative Description Weighted average assumptions used to determine net costs [Abstract] Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Contribute to plans in next year Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months Defined Benefit Plan, Expected Future Benefit Payments, Year Two Defined Benefit Plan, Expected Future Benefit Payments, Year Two Defined Benefit Plan, Expected Future Benefit Payments, Year Three Defined Benefit Plan, Expected Future Benefit Payments, Year Three Defined Benefit Plan, Expected Future Benefit Payments, Year Four Defined Benefit Plan, Expected Future Benefit Payments, Year Four Defined Benefit Plan, Expected Future Benefit Payments, Year Five Defined Benefit Plan, Expected Future Benefit Payments, Year Five Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter Defined Benefit Plan, Target Allocation Percentage Defined Benefit Plan, Target Allocation Percentage Defined Benefit Plan, Investment Strategies, Investment Fund Category Defined Benefit Plan, Investment Strategies, Investment Fund Category Health care cost trend (in hundredths) Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year Health care cost rate declining through Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate Ultimate cost trend rate (in hundredths) Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Effect on total service and interest component, increase Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components Effect on total service and interest component, decrease Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components Effect on post-retirement benefit obligation, increase Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation Effect on post-retirement benefit obligation, decrease Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation Employee Savings Plans [Abstract] Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract] Defined contribution savings plan, cost of plan Defined Contribution Plan, Cost Recognized Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Deferred Compensation Arrangement with Individual, Share-based Payments [Table] Schedule of Deferred Compensation Arrangement with Individual, Share-based Payments [Table] Title of Individual [Axis] Title of Individual [Axis] Title of Individual with Relationship to Entity [Domain] Relationship to Entity [Domain] Director [Member] Director [Member] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Axis] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Domain] Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Domain] Director Deferred Share Units [Member] Deferred Compensation, Share-based Payments [Member] Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items] Director deferred share units [Roll Forward] Director deferred share units [Roll Forward] A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. Director deferred share units, beginning balance (in shares) Deferred compensation arrangement with individual shares outstanding The number of director deferred share units outstanding at the balance sheet date. Director deferred share units, issued (in shares) Deferred Compensation Arrangement with Individual, Shares Issued Director deferred share units, converted (in shares) Deferred Compensation Arrangement With Individual, Shares Converted Shares of Director Deferred Share Units that converted to shares of common stock. Director deferred share units, ending balance (in shares) Weighted-average grant date fair value, director deferred share units, beginning balance (in dollars per share) Weighted-average grant date fair value, director deferred share units, shares outstanding The weighted-average grant date fair value of director deferred share units outstanding. Weighted-average grant date fair value, director deferred share units, issued (in dollars per share) Weighted average grant date fair value director deferred share units shares issued during period The weighted average grant date fair value of director deferred share units issued during the period. Weighted average grant date fair value director deferred share units, converted Weighted Average Grant Date Fair Value Director Deferred Share Units Converted During Period The weighted average grant date fair value of director deferred share units converted during the period. Weighted-average grant date fair value, director deferred share units, ending balance (in dollars per share) Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Other Consolidated Entities [Member] Other Consolidated Entities [Member] Other companies which are controlled, directly or indirectly, by the parent. The usual condition for control is ownership of a majority (over 50%) of the outstanding voting stock. The power to control may also exist with a lesser percentage of ownership, for example, by contract, lease, agreement with other stockholders or by court decree. Secured Debt [Member] Secured Debt [Member] Corporate Debt Securities [Member] Corporate Debt Securities [Member] Senior Notes [Member] Senior Notes [Member] Medium-term Notes [Member] Medium-term Notes [Member] Unsecured Debt [Member] Unsecured Debt [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] General Mortgage Bonds EIRR due 2017-2035 [Member] General Mortgage Bonds EIRR Due 20172035 [Member] General Mortgage bonds EIRR due 2017-2035 General Mortgage bonds Series 2009A due 2019 [Member] General Mortgage bonds Series 2009 due 2019 [Member] General Mortgage bonds Series 2009 due 2019. General Mortgage bonds EIRR series 2005 [Member] General Mortgage bonds EIRR series 2005 [Member] General Mortgage bonds EIRR series 2005 General Mortgage bonds EIRR series 2007B due 2035 [Member] General Mortgage bonds EIRR series 2007B due 2035 [Member] General Mortgage bonds EIRR series 2007B due 2035. Senior notes due 2017 KCPL [Member] Senior notes due 2017 KCPL [Member] Senior notes due 2017 KCPL. Senior notes due 2018 KCPL [Member] Senior notes due 2018 KCPL [Member] Senior notes due 2018 KCPL. Senior Notes due 2023 KCPL [Member] Senior Notes due 2023 KCPL [Member] 3.15% Series Senior Notes due 2023 KCPL [Member] Senior Notes due 2025 KCPL [Member] Senior Notes due 2025 KCPL [Member] Senior Notes due 2025 KCPL [Member] Senior notes due 2035 KCPL [Member] Senior notes due 2035 KCPL [Member] Senior notes due 2035 KCPL. Senior Notes Due 2041 KCPL [Member] Senior Notes Due 2041 KCPL [Member] Senior Notes Due 2041 KCPL. EIRR Bonds Series 2007A and 2007B due 2035 [Member] EIRR Bonds Series 2007A and 2007B due 2035 [Member] EIRR Bonds Series 2007A and 2007B due 2035 [Member] EIRR bonds 2.875 percent Series 2008 [Member] Eirr Bonds 2875 Percent Series 2008 [Member] 2.875 percent EIRR bonds due 2038. First Mortgage Bonds due through 2021 [Member] First Mortgage Bonds due through 2021 [Member] First Mortgage Bonds due through 2021 [Member] First Mortgage Bonds Due20132021 Member First Mortgage Bonds Due20132021 Member First mortgage bonds due 2013-2021. Pollution control bonds Wamego Series 1996 due 2026 [Member] Pollution control bonds Wamego Series 1996 due 2026 [Member] Pollution control bonds Wamego Series 1996 due 2026. Pollution control bonds state environmental 1993 due 2028 [Member] Pollution control bonds state environmental 1993 due 2028 [Member] Pollution control bonds state environmental 1993 due 2028. Pollution control bonds SJLP due 2013 [Member] Pollution control bonds SJLP due 2013 [Member] Pollution control bonds SJLP due 2013. Senior notes 8.27 percent series due 2021 [Member] Senior Notes 827 Percent Series Due 2021 [Member] Senior notes 8.27 percent series due 2021. Medium term notes 7.16 percent series due 2013 [Member] Medium Term Notes 716 Percent Series Due 2013 [Member] Medium term notes 7.16 percent series due 2013. Medium term notes 7.33 percent series due 2023 [Member] Medium Term Notes 733 Percent Series Due 2023 [Member] Medium term notes 7.33 percent series due 2023. Medium term notes 7.17 percent series due 2023 [Member] Medium Term Notes 717 Percent Series Due 2023 [Member] Medium term notes 7.17 percent series due 2023 Senior notes due 2013 [Member] Senior notes due 2013 [Member] Senor notes due 2013. Senior notes due 2017 [Member] Senior notes due 2017 [Member] Senior notes due 2017. Senior Notes Due 2021 [Member] Senior Notes Due 2021 [Member] Senior Notes Due 2021. Senior Notes Due 2022 [Member] Senior Notes Due 2022 [Member] Senior Notes Due 2022. Senior Notes Series A due 2025 [Member] Senior Notes Series A due 2025 [Member] Senior Notes Series A due 2025 Senior Notes Series B due 2033 [Member] Senior Notes Series B due 2033 [Member] Senior Notes Series B due 2033. Senior Notes Series C due 2043 [Member] Senior Notes Series C due 2043 [Member] Senior Notes Series C due 2043. Secured EIRR Bonds Series 2005 [Member] Secured EIRR Bonds Series 2005 [Member] Secured EIRR Bonds Series 2005 [Member] Unsecured EIRR Bonds Series 2005 [Member] Unsecured EIRR Bonds Series 2005 [Member] Unsecured EIRR Bonds Series 2005 [Member] Bridge Loan [Member] Bridge Loan [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Principal outstanding Long-term Debt, Gross EIRR bonds repurchased and held DebtInstrumentCarryingAmountRepurchasedAndHeld Amount of long-term debt before deduction of unamortized discount or premium that has been repurchased and is being held by the issuer. Debt Instrument, Maturity Date Debt Instrument, Maturity Date Debt Instrument Maturity Date Range End Debt Instrument, Maturity Date Range, End Current maturities Long-term Debt, Current Maturities Unamortized discount and premium, net and debt issuance costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Long-term debt excluding current maturities Long-term Debt, Excluding Current Maturities Debt Instrument Maturity Date Range Start Debt Instrument, Maturity Date Range, Start Interest rates (in hundredths) Debt Instrument, Interest Rate, Stated Percentage Long-term Debt, Weighted Average Interest Rate Long-term Debt, Weighted Average Interest Rate Variable rate (in hundredths) Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths) Debt Instrument, Interest Rate, Effective Percentage Amortization of Financing Costs Amortization of Debt Issuance Costs Bonds purchased in lieu of redemption Bonds Purchased In Lieu Of Redemption Environmental Improvement Revenue Refunding bonds that were purchased rather than remarketed by KCP&L Proceeds from Issuance of Senior Long-term Debt Proceeds from Issuance of Senior Long-term Debt Line Of Credit Facility Maximum Borrowing Capacity As Amended Line Of Credit Facility Maximum Borrowing Capacity As Amended Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility, as amended. KCPL Municipal Bond Insurance Policies [Abstract] KCPL Municipal Bond Insurance Policies [Abstract] KCPL Municipal Bond Insurance Policies [Abstract] Principal outstanding covered by insurance policies Principal outstanding covered by insurance policies Principal value of debt instrument outstanding which is covered by a municipal bond insurance policy between KCP and L and Syncora Guarantee, Inc. (Syncora). The insurance agreements beotween KCP and L and Syncora provide for reimbursement by KCP and L for any amounts that Syncora pays under the municipal bond insurance policies. Additional collateral necessary due to issuance of additional mortgage bonds Additional collateral necessary due to issuance of additional mortgage bonds Additional collateral necessary under the insurance agreement due to the issuance of general mortgage bonds in 2009 that resulted in the aggregate amount of outstanding general mortgage bonds exceeding 10% of total capitalization. Insurance Agreement Covenant Description Insurance Agreement Covenant Description Description of minimum financial levels (for example, tangible net worth and working capital) and achievement of certain financial ratios (for example, working capital ratio and debt service coverage ratio), and adherence to certain clauses which generally require or restrict certain actions (for example, entering into a debt arrangement with equal or greater seniority, and selling or discontinuing a certain business segment or material subsidiary) to be in compliance with the covenant clauses of the municipal bond insurance policy. May also include a discussion of the adverse consequences that would result if the entity violates or fails to satisfy the covenants. Insurance Agreement Covenant Compliance Insurance Agreement Covenant Compliance States whether the entity was in compliance with the municipal bond insurance covenants throughout the reporting period, and describes facts and circumstances of any compliance failure. Insurance Agreement Covenant Indebtedness To Total Capitalization Ratio Maximum Insurance Agreement Covenant Indebtedness To Total Capitalization Ratio Maximum The maximum indebtedness to total capitalization ratio permitted under the municipal bond insurance policy. Proportion Of Secured Debt To Total Indebtedness Based On Bond Ratings Maximum In Hundredths Proportion Of Secured Debt To Total Indebtedness Based On Bond Ratings Maximum In Hundredths The maximum proportion of secured debt to total capitalization under which KCP and L may issue additional bonds per its General Mortgage Indenture, if the long-term rating for such bonds by Standard and Poor's or Moody's Investors Service would be at or below A- or A3. If this ratio of secured debt to total capitalization would exceed this amount after giving effect to such additional bonds, no additional bonds may be issued. Aggregate Amount Of Outstanding General Mortgage Bonds As Percentage Of Total Capitalization Maximum In Hundredths Aggregate Amount Of Outstanding General Mortgage Bonds As Percentage Of Total Capitalization Maximum In Hundredths If the aggregate amount of outstanding general mortgage bonds as a percentage of total capitalization exceeds this amount, additional collateral must be provided to the insurance company under the municipal bonds insurance agreement. Long-term Debt, Fiscal Year Maturity [Abstract] Long-term Debt, Fiscal Year Maturity [Abstract] Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months Long-term Debt, Maturities, Repayments of Principal in Year Two Long-term Debt, Maturities, Repayments of Principal in Year Two Long-term Debt, Maturities, Repayments of Principal in Year Three Long-term Debt, Maturities, Repayments of Principal in Year Three Long-term Debt, Maturities, Repayments of Principal in Year Four Long-term Debt, Maturities, Repayments of Principal in Year Four Long-term Debt, Maturities, Repayments of Principal in Year Five Long-term Debt, Maturities, Repayments of Principal in Year Five GMO Senior Notes [Abstract] GMO Senior Notes [Abstract] GMO Senior Notes Debt Instrument, Covenant Description Debt Instrument, Covenant Description Debt Instrument, Covenant Compliance Debt Instrument, Covenant Compliance Regulatory Proceedings [Table] Public Utilities General Disclosures [Table] Regulatory Agency [Axis] Regulatory Agency [Axis] Regulatory Agency [Domain] Regulatory Agency [Domain] Missouri Public Service Commission [Member] MissouriPublicServiceCommission [Member] Information related to the Public Service Commission of the State of Missouri. Kansas Corporation Commission [Member] Kansas Corporation Commission [Member] Information related to the State Corporation Commission of the State of Kansas. Subsegments [Axis] Subsegments [Axis] Subsegments [Domain] Subsegments [Domain] St Joseph Light and Power division [Member] St Joseph Light and Power Division [Member] Information related to St. Joseph Light and Power, a division of GMO. Missouri Public Service division [Member] Missouri Public Service Division [Member] Information related to Missouri Public Service, a division of GMO. Regulatory Proceedings [Line Items] Public Utilities, General Disclosures [Line Items] Annual revenue increase, requested Public Utilities, Requested Rate Increase (Decrease), Amount Revised annual revenue increase, requested Public Utilities, Requested Rate Increase (Decrease), Amended, Amount Annual revenue increase, requested, portion related to rebasing fuel and purchased power expense Public Utilities Requested Rate Increase Decrease Amount, Rebasing Fuel And Purchased Power Expense Amount of public utility's requested rate increase (decrease) amount, the portion related to the rebasing of fuel and purchased power expense Annual revenue increase, requested, not including rebasing fuel and purchased power expense Public Utilities Requested Rate Increase Decrease Amount Not Including Rebasing Fuel And Purchased Power Expense Amount of public utility's requested rate increase (decrease) with regulatory agency, not including rebasing fuel and purchased power expense Return on equity, requested (in hundredths) Public Utilities, Requested Return on Equity, Percentage Revised return on equity, requested (in hundredths) Revised return on equity (in hundredths) Revised return on equity as requested by the company in the pending rate case filed with the state. Rate-making equity ratio, requested (in hundredths) Public Utilities, Requested Equity Capital Structure, Percentage Commission Staff Recommended Return On Equity Percentage Commission Staff Recommended Return On Equity Percentage Percentage of return on equity recommended by staff of the state commission. Commission Staff Recommended Rate Increase (Decrease) Amount Commission Staff Recommended Rate Increase Decrease Amount Amount of rate increase (decrease) recommended by staff of the state commission. Annual revenue increase authorized Public Utilities, Approved Rate Increase (Decrease), Amount Return on equity, approved (in hundredths) Public Utilities, Approved Return on Equity, Percentage Ratemaking equity ratio, approved (in hundredths) Public Utilities, Approved Equity Capital Structure, Percentage Rate making equity ratio after including other comprehensive income, approved Rate making equity ratio after including other comprehensive income, approved The approved equity percentage (including other comprehensive income) of total capitalization used in the rate making process. Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Beginning balance Accumulated Other Comprehensive Income (Loss), Net of Tax Other comprehensive income (loss) before reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified from accumulated other comprehensive loss Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Net current period other comprehensive income Other Comprehensive Income (Loss), Net of Tax Ending balance Statement of Stockholders' Equity [Abstract] Common Stock [Member] Common Stock [Member] Preferred Stock [Member] Preferred Stock [Member] Retained Earnings [Member] Retained Earnings [Member] Treasury Stock [Member] Treasury Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member] AOCI Attributable to Parent [Member] Preference Stock [Member] Preference Stock [Member] Preference stock. Beginning balance Stockholders' Equity Attributable to Parent Beginning balance (in shares) Shares, Issued Beginning balance, treasury stock (in shares) Issuance of stock Stock Issued During Period, Value, New Issues Issuance of stock (in shares) Stock Issued During Period, Shares, New Issues Equity compensation expense, net of forfeitures Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Redemption of cumulative preferred stock Stock Redeemed or Called During Period, Value Redemption of cumulative preferred stock (in shares) Stock Redeemed or Called During Period, Shares Unearned Compensation [Abstract] Unearned Compensation [Abstract] Issuance of restricted common stock AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsIssuance Amount recorded to Additional Paid in Capital to represent unearned compensation related to the issuance of restricted common stock. Forfeiture of restricted common stock AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsForfeitures Amount recorded to Additional Paid in Capital to reduce unearned compensation related to the forfeiture of restricted common stock. Compensation expense recognized Adjustments to Additional Paid in Capital, Share-based Compensation, Restricted Stock Unit or Restricted Stock Award, Requisite Service Period Recognition Other Stockholders' Equity, Other Net income Redemption premium on cumulative preferred stock Preferred Stock Redemption Premium Loss on reissuance of treasury stock Treasury Stock Reissued at Lower than Repurchase Price Dividends: Dividends [Abstract] Common stock ($1.0625, $0.9975 and $0.935 per share) Dividends, Common Stock, Cash Preferred stock - at required rates Dividends, Preferred Stock, Cash Performance shares Dividends, Share-based Compensation, Cash Treasury shares acquired Treasury Stock, Value, Acquired, Cost Method Treasury shares acquired (in shares) Treasury Stock, Shares, Acquired Treasury shares reissued Stock Issued During Period, Value, Treasury Stock Reissued Treasury shares reissued (in shares) Stock Issued During Period, Shares, Treasury Stock Reissued Derivative hedging activity, net of tax Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Change in unrecognized pension expense, net of tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Ending balance Ending balance, treasury stock (in shares) Ending balance (in shares) Preferred Stock 4 Point 50 [Member] Preferred Stock 4 Point 50 [Member] 4.50% Preferred Stock Preferred Stock 4 Point 20 [Member] Preferred Stock 4 Point 20 [Member] 4.20% Preferred Stock Preferred Stock 4 Point 35 [Member] Preferred Stock 4 Point 35 [Member] 4.35% Preferred Stock Current Assets Assets, Current [Abstract] Cash and cash equivalents Time deposit TimeDepositAtCarryingValue Consists of a non-negotiable fixed rate investment in a time deposit with an original maturity of greater than three months and is recorded on the balance sheet at cost. Funds on deposit Deposits Assets, Current Receivables, net Receivables, Net, Current Related party receivables Accounts Receivable, Related Parties, Current Fuel inventories, at average cost Energy Related Inventory Materials and supplies, at average cost Other Inventory, Supplies, Gross Deferred refueling outage costs Deferred refueling outage costs Sum of the carrying amounts of deferred costs for nuclear plant refueling outages that are expected to be recognized as a charge against earnings. Refundable income taxes Income Taxes Receivable, Current Derivative instruments Derivative Asset, Current Assets held for sale Disposal Group, Including Discontinued Operation, Assets, Current Prepaid expenses and other assets Prepaid Expense and Other Assets, Current Total Assets, Current Electric Public Utilities, Property, Plant and Equipment, Plant in Service Less - accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Net utility plant in service Public Utilities, Property, Plant and Equipment in service, Net Period end amount of total net PPE in service Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Nuclear fuel, net of amortization of $172.1 and $192.5 Nuclear Fuel, Net of Amortization Total Public Utilities, Property, Plant and Equipment, Net Investments and Other Assets Investments And Other Assets [Abstract] Nuclear decommissioning trust fund Decommissioning Fund Investments Regulatory assets Regulatory Assets, Noncurrent Goodwill Goodwill Derivative instruments Derivative Asset, Noncurrent Other Other Assets, Noncurrent Total Investments And Other Assets The total of investments and other long-term assets. Total Current Liabilities Liabilities, Current [Abstract] Notes payable Short-term Bank Loans and Notes Payable Commercial paper Commercial Paper Current maturities of long-term debt Accounts payable Accounts Payable, Current Related party payables Accounts Payable, Related Parties, Current Accrued taxes Taxes Payable, Current Accrued interest Interest Payable, Current Accrued compensation and benefits Employee-related Liabilities, Current Pension and post-retirement liability Derivative instruments Derivative Liability, Current Deferred income taxes Deferred Tax Liabilities, Net, Current Other Other Liabilities, Current Total Liabilities, Current Deferred Credits and Other Liabilities Liabilities, Noncurrent [Abstract] Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Deferred tax credits Accumulated Deferred Investment Tax Credit Asset retirement obligations Asset Retirement Obligations, Noncurrent Pension and post-retirement liability Regulatory liabilities Regulatory Liability, Noncurrent Other Other Liabilities, Noncurrent Total Liabilities, Noncurrent Capitalization Shareholders' equity Stockholders' Equity Attributable to Parent [Abstract] Common stock Common Stock, Value, Issued Preferred Stock, Value, Issued Preferred Stock, Value, Issued Retained earnings Retained Earnings (Accumulated Deficit) Treasury stock - 128,087 and 101,229 shares, at cost Treasury Stock, Value Accumulated other comprehensive loss Total shareholders' equity Noncontrolling interest Stockholders' Equity Attributable to Noncontrolling Interest Long-term debt (Note 12) Total Capitalization, Long-term Debt and Equity Commitments and Contingencies (Note 15) Commitments and Contingencies Total Liabilities and Equity Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts, Notes, Loans and Financing Receivable by Receivable Type [Axis] Receivable Type [Axis] Receivable [Domain] Receivable [Domain] Trade Accounts Receivable [Member] Trade Accounts Receivable [Member] Accounts, Notes, Loans and Financing Receivable by Billing Status, Type [Axis] Billing Status, Type [Axis] Receivables Billing Status [Domain] Receivables Billing Status [Domain] Billed Revenues [Member] Billed Revenues [Member] Unbilled Revenues [Member] Unbilled Revenues [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts Receivable, Gross, Current Accounts Receivable, Gross, Current Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Other receivables Other Receivables, Gross, Current Total Offsetting [Abstract] Offsetting Assets [Table] Offsetting Assets [Table] Offsetting Assets [Line Items] Offsetting Assets [Line Items] Derivative Asset, Fair Value, Gross Asset Derivative Asset, Fair Value, Gross Asset Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset Derivative Asset Derivative Asset Derivative, Collateral, Obligation to Return Securities Derivative, Collateral, Obligation to Return Securities Derivative, Collateral, Obligation to Return Cash Derivative, Collateral, Obligation to Return Cash Derivative Asset, Fair Value, Amount Offset Against Collateral Derivative Asset, Fair Value, Amount Offset Against Collateral AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Interest charges Fuel Utilities Operating Expense, Fuel Used Utility operating and maintenance expenses Utilities Operating Expense, Maintenance and Operations Income before income tax expense and income from equity investments Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax benefit Net income Fair Value Disclosures [Abstract] Fair value of assets and liabilities Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Unobservable inputs reconciliation Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Kcpl Greater Missouri Operations Member MissouriPublicServiceCommission [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Excise and Sales Taxes Excise and Sales Taxes Anticipated Acquisition of Westar Energy, Inc. [Abstract] Anticipated Acquisition of Westar Energy, Inc. [Abstract] Anticipated Buiness Combination Disclosure [Text Block] Anticipated Business Combination Disclosure [Text Block] The entire disclosure for an anticipated business combination to be completed in a future period. Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Stockholders' Equity Note [Abstract] Common Shareholders' Equity Stockholders' Equity Note Disclosure [Text Block] Offsetting Liabilities [Abstract] Offsetting Liabilities [Abstract] Offsetting Liabilities [Table] Offsetting Liabilities [Table] Offsetting Liabilities [Line Items] Offsetting Liabilities [Line Items] Derivative Liability, Fair Value, Gross Liability Derivative Liability, Fair Value, Gross Liability Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset Derivative Liability Derivative Liability Derivative, Collateral, Right to Reclaim Securities Derivative, Collateral, Right to Reclaim Securities Derivative, Collateral, Right to Reclaim Cash Derivative, Collateral, Right to Reclaim Cash Derivative Liability, Fair Value, Amount Offset Against Collateral Derivative Liability, Fair Value, Amount Offset Against Collateral Cash collateral posted with counterparties Collateral Already Posted, Aggregate Fair Value Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] 7.25% Mandatory Convertible Preferred Stock, Series A [Member] Series A Preferred Stock [Member] Depositary Shares [Member] Depositary Share [Member] Depositary Share representing 1/20th of a share of 7.00% Mandatory Convertible Preferred Stock, Series B Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Anticipated Acquisition Of Westar Energy, Inc. [Line Items] Anticipated Acquisition Of Westar Energy, Inc. Cash consideration to be transferred (per share) AnticipatedBusinessCombinationCashConsiderationToBeTransferred Amount of cash consideration per share of the acquiree to be transferred by the acquirer. Great Plains Energy Average Stock Price - Maximum If the Great Plains Energy Average Stock Price is greater than this amount, the Exchange Ratio will be 0.2709. Great Plains Energy Average Stock Price - Less Than Maximum, Greater Than Minimum If the Great Plains Energy Average Stock Price is equal to or between these amounts, the Exchange Ratio will be an amount equal to the quotient obtained by dividing (x) $9.00 by (y) the Great Plains Energy Average Stock Price. Great Plains Energy Average Stock Price Minimum If the Great Plains Energy Average Stock Price is less than this amount, the Exchange Ratio will be 0.3148. Exchange Ratio if Great Plains Energy Avg Stock Price is less than $28.5918 ExchangeRatio2 Exchange Ratio if the Great Plains Energy Average Stock Price is less than $28.5918. Exchange Ratio if Great Plains Energy Avg Stock Price is greater than $33.2283 Exchange Ratio1 Exchange ratio if the Great Plains Energy Average Stock Price is greater than $33.2283. Exchange Ratio Numerator Exchange Ratio Numerator Amount to be divided by the Great Plains Energy Average Stock Price if the Great Plains Energy Average Stock Price is greater than or equal to $28.5918 but less than or equal to $33.2283. Preferred Shares To Be Issued, Stock Purchase Agreement, Series A Preferred Stock Preferred Shares To Be Issued, Stock Purchase Agreement, Series A Preferred Stock Number of 7.25% Mandatory Convertible Preferred Stock, Series A shares to be issued under the stock purchase agreement with OMERS. Preferred Stock, Purchase Agreement, Proceeds Preferred Stock, Purchase Agreement, Proceeds Amount of proceeds to be received for sale of 7.25% Mandatory Convertible Preferred Stock, Series A, without par value at the closing of the merger. Stock Issued During Period, Shares, New Issues Shares Issued, Price Per Share Shares Issued, Price Per Share Net Proceeds from Issuance of Depositary Shares NetProceedsFromIssuanceOfDepositaryShares Net proceeds from the issuance of depositary shares Net Proceeds from Issuance of Common Stock NetProceedsFromIssuanceOfCommonStock Net proceeds from issuance of common stock Gross Proceeds from Issuance of Depositary Shares ProceedsFromIssuanceOfDepositaryShares Proceeds from the issuance of depositary shares (representing 1/20th of a share of 7.00% Mandatory Convertible Preferred Stock, Series B) Gross Proceeds from Issuance of Common Stock Amount of bridge facility Line of Credit Facility, Maximum Borrowing Capacity Amount of bridge facility, as amended Anticipated Acquisition Financing, Mandatory Convertible Preferred Equity Anticipated Acquisition Financing Mandatory Convertible Preferred Equity Anticipated amount of mandatory convertible preferred equity to be issued to finance a portion of the cash consideration for the merger. Anticipated Acquisition Financing, Common And Preferred Equity Anticipated Acquisition Financing Common And Preferred Equity Anticipated amount of common and preferred equity to be issued to finance a portion of the cash consideration for the merger. Anticipated Acquisition Financing, Debt AnticipatedAcquisitionFinancingDebt Anticipated amount of long-term debt to be issued to finance a portion of the cash consideration for the merger. Merger Termination Fee, Regulatory Approval Merger Termination Fee Regulatory Approval Fee that Great Plains Energy may be required to pay if the termination of the Merger Agreement under specified circumstances relating to a failure to obtain required regulatory approvals prior to May 31, 2017 (which date may be extended to November 30, 2017 under certain circumstances), a final and nonappealable order enjoining the consummation of the merger in connection with regulatory approvals or failure by Great Plains Energy to consummate the merger once all of the conditions have been satisfied. Merger Termination Fee Great Plains Energy MergerTerminationFeeGreatPlainsEnergy Termination fee that could result in the event that the Merger Agreement is terminated by (a) either party because the closing has not occurred by the End Date or (b) Westar, as a result of Great Plains Energy's uncured breach of the Merger Agreement, and prior to such termination, an acquisition proposal for Great Plains Energy is publicly disclosed or made to Great Plains Energy, if Great Plains Energy enters into an agreement or consummates a transaction with respect to an acquisition proposal within twelve months following such termination. Merger Termination Fee, Great Plains Energy Board of Directors Merger Termination Fee - Great Plains Energy Board of Directors Fee Great Plains Energy may be required to pay if the Merger Agreement is terminated by Westar as a result of the Great Plains Energy board of directors changing its recommendation to the Great Plains Energy shareholders as a result of a superior proposal prior to the Great Plains Energy shareholder approval having been obtained. Merger Termination Fee, Great Plains Energy Shareholders Merger Termination Fee - Great Plains Energy Shareholders Fee Great Plains Energy may be required to pay if the Merger Agreement is terminated by either Great Plains Energy or Westar as a result of the Great Plains Energy shareholders not approving the issuance of the Great Plains Energy Common Stock to the Westar shareholders in the merger. Merger Termination Fee, Superior Proposal Merger Termination Fee Superior Proposal Fee Westar may be required to pay if the Merger Agreement is terminated by Westar under specified circumstances to enter into a definitive acquisition agreement with respect to a superior proposal or by Great Plains Energy as a result of Westar's board of directors changing its recommendation of the merger prior to the Westar shareholder approval having been obtained. Merger Termination Fee Westar MergerTerminationFeeWestar Termination fee that could result in the event that the Merger Agreement is terminated by (x) either party because the closing has not occurred by the End Date or (y) Great Plains Energy, as a result of Westar's uncured breach of the Merger Agreement, and prior to such termination, an acquisition proposal for Westar is publicly disclosed or made to Westar, if Westar enters into an agreement or consummates a transaction with respect to an acquisition proposal within twelve months following such termination, then Westar may be required to pay Great Plains Energy a termination fee. Preferred Stock 3 Point 80 [Member] Preferred Stock 3 Point 80 [Member] 3.80% Preferred Stock Preference Stock Convertible Preferred Stock [Member] Cash and Cash Equivalents, at Carrying Value Time deposit Time Deposits, at Carrying Value Accounts receivable from subsidiaries Notes receivable from subsidiaries, current Notes Receivable, Related Parties, Current Money pool receivable Amount receivable under the Great Plains Energy money pool, an internal financing arrangement. Taxes receivable Derivative Asset, Current Other current assets Other Assets, Current Total Investment in KCP&L Investment in KCPL This item represents the carrying amount of Great Plains Energy's investment in KCPL, its other reporting consolidated subsidiary, presented as an equity method investment for stand-alone presentation of the parent company. Investment in other subsidiaries Investment in other subsidiaries This item represents the carrying amount of Great Plains Energy's investments in other subsidiaries (other than KCPL) presented as equity method investments for stand-alond reporting of the parent company. Notes receivable from subsidiaries, noncurrent Notes Receivable, Related Parties, Noncurrent Deferred income taxes Deferred Tax Assets, Net, Noncurrent Total investments and other assets Assets, Noncurrent Accounts payable to subsidiaries Due to Related Parties, Current Total Liabilities, Noncurrent, Total Capitalization Capitalization, Long-term Debt and Equity [Abstract] Common stock Accumulated Other Comprehensive Income (Loss), Net of Tax Commitments and Contingencies Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] Current income taxes Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Total Current Income Tax Expense (Benefit) Deferred income taxes Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Total Noncurrent income taxes Noncurrent Income Tax Expense Benefit Continuing Operations [Abstract] Federal Noncurrent Federal Tax Expense Benefit The noncurrent component of income tax expense for the period representing amounts paid or payable (or refundable) as determined by applying the provisions of enacted federal tax law to the domestic taxable Income or Loss from continuing operations. State Noncurrent State And Local Tax Expense Benefit The noncurrent component of income tax expense for the period representing amounts paid or payable (or refundable) as determined by applying the provisions of enacted state and local tax law to relevant amounts of taxable Income or Loss from continuing operations. Foreign Noncurrent Foreign Tax Expense Benefit The noncurrent component of income tax expense for the period representing amounts paid or payable (or refundable) as determined by applying the provisions of foreign enacted tax law to the foreign taxable Income or Loss from continuing operations. Total Noncurrent Income Tax Expense Benefit The noncurrent component of income tax expense for the period representing amounts of income taxes paid or payable (or refundable) for the period for all income tax obligations as determined by applying the provisions of relevant enacted tax laws to relevant amounts of taxable Income or Loss from continuing operations. Investment tax credit Investment tax credit [Abstract] Deferral Investment Tax Credit Deferral The amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; the part related to the deferral of investment tax credits. Amortization Investment Tax Credit Amortization The amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; the part related to the amortization of investment tax credits. Total Investment Tax Credit, Total Total investment tax credit included in current tax expense. Total income tax expense Effective Income Tax Rate Reconciliation, Percent [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] Federal statutory income tax (in hundredths) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Differences between book and tax depreciation not normalized (in hundredths) Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation, Percent Amortization of investments tax credits (in hundredths) Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Percent Federal income tax credits (in hundredths) Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent State income taxes (in hundredths) Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Changes in uncertain tax positions, net (in hundredths) Effective Income Tax Rate Reconciliation, Tax Contingency, Percent Transaction costs (in hundredths) EffectiveIncomeTaxRateReconciliationNondeductibleExpenseTransactionCosts Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to transaction costs Valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Other (in hundredths) Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective income tax rate (in hundredths) Effective Income Tax Rate Reconciliation, Percent Derivative Instruments and Hedging Activities Disclosure [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] Relationship to Entity [Domain] Equity compensation expense and associated income tax benefits Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Performance share activity Schedule of Nonvested Performance-based Units Activity [Table Text Block] Restricted stock activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Director Deferred Share Units Schedule of Deferred Compensation Arrangement with Individual, Share-based Payments [Table Text Block] Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Short-term Debt [Line Items] Short-term Debt [Line Items] Line of Credit Facility, Maximum Borrowing Capacity Revolving credit facility expiration date Line of Credit Facility, Expiration Date Maximum borrowing capacity with transfer of unused commitments Line Of Credit Facility Maximum Borrowing Capacity With Transfer Of Unused Commitments The maximum amount of lending capacity under Great Plains Energy's credit facility if unused commitments are transferred between that credit facility and the credit facilities of KCPL and GMO Maximum transfer of unused commitments Line Of Credit Facility Maximum Transfer Of Unused Commitments The maximum amount of unused commitments that can be transferred between the entity's revolving credit facility and Great Plains Energy's revolving credit facility. Line of Credit Facility, Covenant Terms Line of Credit Facility, Covenant Terms Line of Credit Facility, Covenant Compliance Line of Credit Facility, Covenant Compliance Amount of outstanding cash borrowings Commercial paper outstanding Weighted-average interest rate from outstanding borrowings Short-term Debt, Weighted Average Interest Rate Amount of letters of credit outstanding Letters of Credit Outstanding, Amount Related Party Transactions and Relationships Related Party Transactions Disclosure [Text Block] Stock Transactions, Parenthetical Disclosures [Abstract] Stock Transactions, Parenthetical Disclosures [Abstract] Common Stock, Dividends, Per Share, Declared Common Stock, Dividends, Per Share, Declared Nuclear Plant [Abstract] Nuclear Plant [Table] Nuclear Plant [Table] Disclosures regarding the nuclear plant including decommissioning costs and nuclear insurance Nuclear Plant [Member] Nuclear Plant [Member] Jointly Owned Utility Plant Interests [Line Items] Jointly Owned Utility Plant Interests [Line Items] Ownership percentage in Wolf Creek, a nuclear generating unit (in hundredths) Nuclear decommissioning trust [Abstract] Nuclear decommissioning trust [Abstract] Nuclear decommissioning trust fund [Roll Forward] Nuclear decommissioning trust fund [Roll Forward] Nuclear decommissioning trust fund [Roll Forward] Beginning balance January 1 Contributions Contributions To Decommissioning Trust Fund This represents total contributions to the decommissioning trust fund during the current period. Earned income, net of fees Decommissioning Trust Fund Earned Income Net Of Fees This represents income earned, net of fees, on decommissioning trust fund investments during the current period. Net realized gains Net Realized Gains Losses On Decommissioning Trust Fund This represents the net realized gains (losses) on decommissioning trust fund investments during the current period. Net unrealized gains (losses) Net Unrealized Gains Losses On Decommissioning Trust Fund This represents the net unrealized gains (losses) on decommissioning trust fund investments during the current period. Ending balance December 31 Nuclear Plant Decommissioning Costs [Abstract] Nuclear Plant Decommissioning Costs [Abstract] Nuclear Plant Decommissioning Costs [Abstract] Current cost of decommissioning (in 2014 dollars) Current Cost Of Decommissioning In 2014 Dollars Represents the current cost of decommissioning the Wolf Creek generation station. Future cost of decommissioning (in 2045 through 2053 dollars) Future cost of decommissioning (in 2045-2053 dollars) This represents the cost of decommissioning the Wolf Creek generating station in expected dollars at the time of decommissioning. Annual Escalation Factor Annual Escalation Factor Annual escalation factor applied to decommissioning costs in current year dollars to arrive at future costs of decommissioning. Annual return on trust assets through 2025 Annual return on trust assets through 2025 This represents the expected rate of return on assets held in the nuclear decommissioning trust through 2025. Annual return on trusts assets in 2053 AnnualReturnOnTrustsAssetsIn2053 The expected rate of return on assets held in the nuclear decommissioning trust is expected to decline to this amount after 2025 through 2053 as the fund's investment mix will increasingly become more conservative as the decommissioning period approaches. Nuclear Insurance [Abstract] Nuclear Insurance [Abstract] Nuclear Insurance [Abstract] Industry aggregate limit on nuclear insurance for property claims including accidental damages Industry Aggregate Limit On Nuclear Insurance For Property Claims Including Accidental Damages Industry aggregate limit on nuclear insurance for property claims related to nuclear acts of terrorism including accidental outage power costs. Industry aggregate limit on non-nuclear acts of terrorism Industry Aggregate Limit On Non-Nuclear Acts Of Terrorism Industry aggregate limit for property claims related to non-nuclear acts of terrorism. Amount of insurance against public liability claims resulting from nuclear incidents to full limit of public liability Amount of insurance against public liability claims resulting from nuclear incidents to full limit of public liability Amount of insurance against public liability claims resulting from nuclear incidents to the full limit of public liability. Maximum available commercial insurance Maximum available commercial insurance Maximum available commercial insurance. Remaining balance provided through industry wide retrospective assesment program mandated by law Remaining balance provided through industry wide retrospective assesment program mandated by law Remaining balance of public liability limits provided through industry wide retrospective assesment program mandated by law. Maximum amount able to be assessed to owners Maximum amount able to be assessed to owners Maximum amount able to be assessed to owners. SFP Program-annual amount payable per incident SFP Program-annual amount payable per incident Under the Secondary Financial Protection (SPF) program, amount that owners can be assessed per nuclear incident per year. Amount of decontamination liability, premature decommissioning liability and property damage insurance Amount of decontamination liability, premature decommissioning liability and property damage insurance Amount of decontamination liability, premature decommissioning liability and property damage insurance. Premature decommissioning coverage applies only if property damage exceeds this amount and trust funds have been exhausted Premature decommissioning coverage applies only if property damage exceeds this amount and trust funds have been exhausted Premature decommissioning coverage applies only if property damage exceeds this amount and trust funds have been exhausted. Estimated maximum amount of retrospective assessments under the current policies Estimated maximum amount of retrospective assessments under the current policies Estimated maximum amount of retrospective assessments under the current policies. Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Computer Software, Intangible Asset [Member] Computer Software, Intangible Asset [Member] Asset Improvements [Member] Other Intangible Assets [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets, Gross Finite-Lived Intangible Assets, Gross Finite-Lived Intangible Assets, Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Amortization of Intangible Assets Amortization of Intangible Assets Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months Finite-Lived Intangible Assets, Amortization Expense, Year Two Finite-Lived Intangible Assets, Amortization Expense, Year Two Finite-Lived Intangible Assets, Amortization Expense, Year Three Finite-Lived Intangible Assets, Amortization Expense, Year Three Finite-Lived Intangible Assets, Amortization Expense, Year Four Finite-Lived Intangible Assets, Amortization Expense, Year Four Finite-Lived Intangible Assets, Amortization Expense, Year Five Finite-Lived Intangible Assets, Amortization Expense, Year Five Investments in nuclear decommissioning trust fund [Table] Schedule of Available-for-sale Securities [Table] Investments in decommissioning trust fund [Axis] Major Types of Debt and Equity Securities [Axis] Investments in decommissioning trust fund [Domain] Major Types of Debt and Equity Securities [Domain] Equity Securities [Member] Equity Securities [Member] Debt Securities [Member] Debt Securities [Member] Other Securities [Member] Other Securities [Member] This category includes information about securities other than equity or debt type securities that will be realized in a short period of time, usually less than one year or the normal operating cycle, whichever is longer. Investments in decommissioning trust fund [Line Items] Schedule of Available-for-sale Securities [Line Items] Cost Basis Available-for-sale Securities, Amortized Cost Basis Unrealized Gains Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax Unrealized Losses Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Unrealized Losses Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Unrealized Gains Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax Unrealized Losses Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Fair Value Weighted average maturity of debt securities (in years) Weighted Average Maturity Of Debt Securities This represents the weighted average number of years when the debt securities held in the decommissioning trust fund are scheduled to be fully repaid. Realized gains Available-for-sale Securities, Gross Realized Gains Realized losses Available-for-sale Securities, Gross Realized Losses Operating income Operating Income (Loss) Basic and diluted earnings per common share Earnings Per Share, Basic and Diluted Basic EPS Earnings Per Share, Basic Diluted EPS Earnings Per Share, Diluted Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Summary of Income Tax Contingencies [Table Text Block] Summary of Income Tax Contingencies [Table Text Block] Subsequent Event, Description Subsequent Event, Description Pollution control bonds Wamego Series 1996 due 2026 [Member] Pollution control bonds state environmental 1993 due 2028 [Member] Subsequent Event, Date Subsequent Event, Date Accumulated Other Comprehensive Income (Loss) [Text Block] Comprehensive Income (Loss) Note [Text Block] Statement of Financial Position (Parenthetical) [Abstract] Statement of Financial Position (Parenthetical) [Abstract] Nuclear Fuel Accumulated Amortization Common Stock, Shares Authorized Common Stock, Shares, Issued Treasury Stock, Shares Preferred Stock, Shares Authorized Preferred Stock, Liquidation Preference, Value Preferred Stock, Liquidation Preference, Value Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Preferred Stock [Text Block] Preferred Stock [Text Block] Long-Term Debt Long-term Debt [Text Block] Pension Plans and Other Employee Benefits Pension and Other Postretirement Benefits Disclosure [Text Block] Schedule of Net Benefit Costs [Table Text Block] Schedule of Net Benefit Costs [Table Text Block] Schedule of Net Funded Status [Table Text Block] Schedule of Net Funded Status [Table Text Block] Schedule Of Periodic Benefit Obligation And Accumulated Benefit Obligation And Fair Value Of Plan Assets By Funded And Under Funded Plans [Table Text Block] Schedule Of Periodic Benefit Obligation And Accumulated Benefit Obligation And Fair Value Of Plan Assets By Funded And Under Funded Plans [Table Text Block] Tabular disclosure of periodic benefit obligation and accumulated benefit obligation and the fair value of plan assets by funded and under funded plans. Schedule of Assumptions Used [Table Text Block] Schedule of Assumptions Used [Table Text Block] Schedule of Expected Benefit Payments [Table Text Block] Schedule of Expected Benefit Payments [Table Text Block] Schedule of Allocation of Plan Assets [Table Text Block] Schedule of Allocation of Plan Assets [Table Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block] Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block] Jointly Owned Electric Utility Plants [Abstract] Jointly Owned Utility Plant Interests [Table] Jointly Owned Utility Plant Interests [Table] Jeffrey Energy Center [Member] Jointly Owned Electricity Generation Plant Jeffrey Energy Center [Member] Information on the jointly owned Jeffrey Energy Center electric utility plant. Iatan Common [Member] Jointly Owned Electricity Generation Plant Iatan Common [Member] Information on the jointly owned Iatan Common electric utility plant. Iatan No. 2 [Member] Jointly Owned Electricity Generation Plant Iatan No. 2 [Member] Information on the jointly owned Iatan No. 2 electric utility plant. Utility plant in service Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service Accumulated depreciation Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation Nuclear fuel, net Construction work in progress Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress Accredited capacity Accredited Capacity The accredited capacity of the jointly owned electric utility plant, in megawatts. Regulatory Matters Public Utilities Disclosure [Text Block] Values of open positions for derivative instruments [Table Text Block] Schedule of Derivative Instruments [Table Text Block] Fair value of open derivative positions, gross values before netting agreements and netting of cash collateral [Table Text Block] Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Offsetting Derivative Assets and Liabilities [Table Text Block] Offsetting Derivative Assets and Liabilities [Table Text Block] [Table Text Block] for Tabular disclosure of derivative assets and liabilities that are subject to offsetting, including master netting arrangements. [Table] Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block] Segment Financial Information [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Performance Shares [Member] Performance Shares [Member] Restricted Stock [Member] Restricted Stock [Member] Stock Options [Member] Employee Stock Option [Member] Equity Units [Member] Equity Unit Purchase Agreements [Member] Assumed conversion of Series B Preferred Stock [Member] AssumedConversionOfPreferredStock [Member] Assumed conversion of Series B preferred stock Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Pension Plans Fair Value Disclosure [Abstract] Pension Plans Fair Value Disclosure [Abstract] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 3 [Member] Defined Benefit Plan, Asset Categories [Axis] Defined Benefit Plan, Asset Categories [Axis] Plan Asset Categories [Domain] Plan Asset Categories [Domain] Real Estate [Member] Real Estate [Member] Hedge Funds [Member] Hedge Funds [Member] US Equity Securities [Member] US Equity Securities [Member] This category includes information about ownership interests or the right to acquire ownership interests in United States' corporations and other legal entities which ownership interest is represented by shares of common or preferred stock (which is neither mandatorily redeemable no redeemable at the option of the holder), convertible securities, stock rights, or stock warrants. International Equity Securities [Member] International Equity Securities [Member] This category includes information about ownership interests or the right to acquire ownership interests in foreign corporations and other legal entities which ownership interest is represented by shares of common or preferred stock (which is neither mandatorily redeemable no redeemable at the option of the holder), convertible securities, stock rights, or stock warrants. Fixed Income Funds [Member] Fixed Income Funds [Member] US Treasury [Member] US Treasury Securities [Member] US Agency, State and Political Subdivisions Debt Securities [Member] US Agency, State and Political Subdivisions Debt Securities [Member] This category includes information about bonds or similar securities issued by state, city, or local governments or the agencies operated by federal, state, city, or local governments. US corporate bonds [Member] Domestic Corporate Debt Securities [Member] Foreign corporate bonds [Member] Foreign Corporate Debt Securities [Member] Cash and Cash Equivalents [Member] Cash and Cash Equivalents [Member] US States and Political Subdivisions Debt Securities [Member] US States and Political Subdivisions Debt Securities [Member] Other Plan Investments [Member] Other Plan Investments [Member] Other benefit plan investments. Institutional Common Collective Trust Funds [Member] Institutional Common Collective Trust Funds [Member] This category is used for institutional common/collective trust funds valued at daily Net Asset Values per share. Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Traded Mutual Funds [Member] Traded Mutual Funds [Member] This category is comprised of traded mutual funds that are valued at daily listed prices. Common Stock and Exchange Traded Funds [Member] Common Stock and Exchange Traded Funds [Member] Investments in traded common stocks or investments that follow an index, commodity or basket of assets that trades similar to a stock on an exchange. American Depository Receipts Global Depository Receipts and Ordinary Shares [Member] AmericanDepositoryReceiptsGlobalDepositoryReceiptsAndOrdinaryShares [Member] Investments in foreign companies held in traded American Depository Receipts, Global Depository Receipts, and/or ordinary shares of stock. Real Estate Investment Trust [Member] Real Estate Investment Trust [Member] Investments in traded Real Estate Investment Trusts. Limited Partnerships [Member] Limited Partnerships [Member] Investments in limited partnerships. Equity Funds [Member] Equity Funds [Member] Corporate Bonds [Member] Corporate Bond Securities [Member] Collateralized Mortgage Obligation Securities [Member] Collateralized Mortgage Backed Securities [Member] Asset-backed Securities [Member] Asset-backed Securities [Member] Fair Value, Plan Assets Alternative Investments, Fair Value Disclosure Alternative Investments, Fair Value Disclosure Fair value measurement with unobservable inputs [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Actual return on plan assets [Abstract] Actual return on plan assets [Abstract] Balance at beginning of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Relating to assets still held Defined Benefit Plan, Actual Return on Plan Assets Still Held Relating to assets sold Defined Benefit Plan, Actual Return on Plan Assets Sold During Period Purchase, sales and settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) Balance at end of period Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value, Measurements, Recurring [Member] Other Great Plains [Member] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Derivative Financial Instruments, Assets [Member] Derivative Financial Instruments, Assets [Member] US Treasury and Government [Member] US Treasury and Government [Member] US Government Corporations and Agencies Securities [Member] US Government Corporations and Agencies Securities [Member] Foreign Government Debt Securities [Member] Foreign Government Debt Securities [Member] Cash Equivalents [Member] Cash Equivalents [Member] Other Trust Assets [Member] Other Trust Assets [Member] Other assets within the trust fund. Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets [Abstract] Assets, Fair Value Disclosure [Abstract] Derivative instruments, assets Decommissioning Fund Investments, Fair Value Decommissioning Fund Investments, Fair Value Self-insured health plan trust [Abstract] Self-insured health plan trust [Abstract] Self-insured health plan trust [Abstract] Self Insured Health Plan Trust Fair Value Disclosure Self Insured Health Plan Trust Fair Value Disclosure The fair value of investments held in a trust for KCP&L's self-insurance health plan. SERP rabbi trust [Abstract] SERP rabbi trust [Abstract] SERP Rabbi Trusts, Fair Value Disclosure Serp Rabbi Trusts Fair Value Disclosure The fair value of equity investments held in rabbi trusts related to GMO's Supplemental Executive Retirement Plan (SERP). Total assets Assets, Fair Value Disclosure, Recurring Liabilities [Abstract] Liabilities, Fair Value Disclosure [Abstract] Derivative instruments, liabilities Fair Value Inputs, Contingency Factor Fair Value Inputs, Contingency Factor Contingency factor used to discount the calculated net present value by the amount management believes is representative of what a market participant would use in valuing the instruments in order to account for the contingent nature of the settlement of the instruments. Total liabilities Liabilities, Fair Value Disclosure, Recurring Valuation and Qualifying Accounts [Abstract] Schedule II Valuation and Qualifying Accounts Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Uncertain Tax Positions Disclosure [Abstract] Uncertain Tax Positions Disclosure [Abstract] Income Tax Contingency [Table] Income Tax Contingency [Table] Uncertain Tax Positions [Line Items] Income Tax Contingency [Line Items] Amount expected to impact the effective tax rate if recognized Unrecognized Tax Benefits that Would Impact Effective Tax Rate Unrecognized Tax Benefits, Period Decrease Unrecognized Tax Benefits, Period Increase (Decrease) Unrecognized tax benefit decrease related to former GMO non-regulated operations Unrecognized tax benefit increase (decrease) related to former GMO non-regulated operations Increase or decrease in unrecognized tax benefits related to former GMO non-regulated operations. Unrecognized Tax Benefits, Income Tax Penalties Accrued Unrecognized Tax Benefits, Income Tax Penalties Accrued Unrecognized Tax Benefits, Interest on Income Taxes Accrued Unrecognized Tax Benefits, Interest on Income Taxes Accrued Interest expense related to unrecognized tax benefits Unrecognized Tax Benefits, Interest on Income Taxes Expense Amount of unrecognized tax benefits that may be recognized in the next twelve months due to statute expirations or settlement agreements with tax authorities Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit Amount of unrecognized tax benefits expected to decrease in the third quarter of 2013 due to new IRS accounting guidance provided to the Company Significant Change In Unrecognized Tax Benefits Expected Amount Of Unrecorded Benefit The amount of the unrecognized tax benefit of a position taken for which it is expected that the total amount thereof will significantly increase or decrease in the third quarter of 2013. Uncertain tax position increase (decrease) related to temporary differences Uncertain Tax Position Increase Decrease Related To Temporary Differences Uncertain tax position increase (decrease) related to temporary differences. Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Balance at beginning of period Unrecognized Tax Benefits Additions for current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Reductions for current year tax positions Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions Additions for prior year tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Reductions for prior year tax positions Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Settlements Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Statute expirations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Foreign currency translation adjustments Unrecognized Tax Benefits, Decrease Resulting from Foreign Currency Translation Balance at end of period Guarantees [Text Block] Guarantees [Text Block] Asset Retirement Obligation Disclosure [Abstract] Asset Retirement Obligations [Text Block] Asset Retirement Obligation Disclosure [Text Block] Schedule of Debt [Table Text Block] Schedule of Debt [Table Text Block] Amortization Of Debt Expense [Table Text Block] Amortization Of Debt Expense [Table Text Block] Tabular disclosure of the component of interest expense representing noncash expenses charged against earnings in the period to amortize debt discount and premium associated with the related debt instruments. Schedule of Maturities of Long-term Debt [Table Text Block] Schedule of Maturities of Long-term Debt [Table Text Block] Unrecorded Unconditional Purchase Obligation and Lease Commitments [Table] Unrecorded Unconditional Purchase Obligation and Lease Commitments [Table] Describes each unrecorded unconditional purchase obligation arrangement to purchase goods and services that extend over multiple periods, any assets pledged to secure payment, any lease commitments (capital or operating) and the fixed or determinable amount of payments due in each of the next five years and thereafter. Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Public Utilities, Inventory, Fuel [Member] Public Utilities, Inventory, Fuel [Member] Purchased Power [Member] Purchased Power [Member] Commitments for purchased power. Capacity [Member] Capacity [Member] Non-regulated natural gas transportation [Member] Non-regulated natural gas transportation [Member] Commitments for non-regulated natural gas transportation. La Cygne Environmental Project [Member] La Cygne Environmental Project [Member] Commitments related to the La Cygne Environmental Project. Other purchase commitments [Member] Other purchase commitments [Member] Purchase commitments for other items not otherwise disclosed in the taxonomy. Unrecorded Unconditional Purchase Obligations and Lease Commitments [Line Items] Unrecorded Unconditional Purchase Obligation [Line Items] Lease Expense [Abstract] Leases [Abstract] Lease expense Operating Leases, Rent Expense, Net Operating Leases [Abstract] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Operating Leases, Future Minimum Payments Due, Next Twelve Months Operating Leases, Future Minimum Payments Due, Next Twelve Months Operating Leases, Future Minimum Payments, Due in Two Years Operating Leases, Future Minimum Payments, Due in Two Years Operating Leases, Future Minimum Payments, Due in Three Years Operating Leases, Future Minimum Payments, Due in Three Years Operating Leases, Future Minimum Payments, Due in Four Years Operating Leases, Future Minimum Payments, Due in Four Years Operating Leases, Future Minimum Payments, Due in Five Years Operating Leases, Future Minimum Payments, Due in Five Years Operating Leases, Future Minimum Payments, Due Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Operating Leases, Future Minimum Payments Due, Total Operating Leases, Future Minimum Payments Due Capital Leases [Abstract] Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Capital Leases, Future Minimum Payments Due, Next Twelve Months Capital Leases, Future Minimum Payments Due, Next Twelve Months Capital Leases, Future Minimum Payments Due in Two Years Capital Leases, Future Minimum Payments Due in Two Years Capital Leases, Future Minimum Payments Due in Three Years Capital Leases, Future Minimum Payments Due in Three Years Capital Leases, Future Minimum Payments Due in Four Years Capital Leases, Future Minimum Payments Due in Four Years Capital Leases, Future Minimum Payments Due in Five Years Capital Leases, Future Minimum Payments Due in Five Years Capital Leases, Future Minimum Payments Due Thereafter Capital Leases, Future Minimum Payments Due Thereafter Capital Leases, Future Minimum Payments Due, Total Capital Leases, Future Minimum Payments Due Purchase Commitments [Abstract] Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract] Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months Unrecorded Unconditional Purchase Obligation, Due within Two Years Unrecorded Unconditional Purchase Obligation, Due within Two Years Unrecorded Unconditional Purchase Obligation, Due within Three Years Unrecorded Unconditional Purchase Obligation, Due within Three Years Unrecorded Unconditional Purchase Obligation, Due within Four Years Unrecorded Unconditional Purchase Obligation, Due within Four Years Unrecorded Unconditional Purchase Obligation, Due within Five Years Unrecorded Unconditional Purchase Obligation, Due within Five Years Unrecorded Unconditional Purchase Obligation, Due after Five Years Unrecorded Unconditional Purchase Obligation, Due after Five Years Unrecorded Unconditional Purchase Obligation, Total Unrecorded Unconditional Purchase Obligation Total Commitments [Abstract] Total Commitments [Abstract] Total Commitments [Abstract] Total Commitments, Due in Next Twelve Months Total Commitments, Due in Next Twelve Months The aggregate amount of operating and capital lease payments and unconditional purchase obligations due in the twelve months after the balance sheet date. Total Commitments, Due within Two Years Total Commitments, Due within Two Years The aggregate amount of operating and capital lease payments and unconditional purchase obligations due in the second year after the balance sheet date. Total Commitments, Due within Three Years Total Commitments, Due within Three Years The aggregate amount of operating and capital lease payments and unconditional purchase obligations due in the third year after the balance sheet date. Total Commitments, Due within Four Years Total Commitments, Due within Four Years The aggregate amount of operating and capital lease payments and unconditional purchase obligations due in the fourth year after the balance sheet date. Total Commitments, Due within Five Years Total Commitments, Due within Five Years The aggregate amount of operating and capital lease payments and unconditional purchase obligations due in the fifth year after the balance sheet date. Total Commitments, Due Thereafter Total Commitments, Due Thereafter The aggregate amount of operating and capital lease payments and unconditional purchase obligations due following the fifth year after the balance sheet date. Total Commitments Due Total Commitments Due The aggregate amount of operating and capital lease payments and unconditional purchase obligations due. Reimbursement by Other Owners per Year (2017) Reimbursement By Other Owners in 2017 Reimbursement By Other Owners in 2017 Reimbursement By Other Owners per Year (2018) Reimbursement By Other Owners in 2018 Reimbursement By Other Owners in 2018 Reimbursements by Other Owners per Year (2019 to 2025) Reimbursements By Other Owners Per Year (2018 To 2025) Reimbursements By Other Owners Per Year (2018 To 2025) Reimbursements by Other Owners Total Reimbursements by Other Owners Total Total reimbursement by other owners to KCP and L for leased property, plant, or equipment. Capacity Sales Agreements per Year 2016 Capacity Sales Agreements per Year 2016 Capacity Sales Agreements per Year 2016 Capacity Sales Agreements per Year 2017 Capacity Sales Agreements per Year 2017 Capacity Sales Agreements per Year 2017 Capacity Sales Agreements per Year 2018 Capacity Sales Agreements per Year 2018 Capacity Sales Agreements per Year 2018 Capacity Sales Agreements per Year 2019 Capacity Sales Agreements Per Year 2019 Capacity sales agreements entered into by KCP&L for 2019 Capacity Sales Agreements per Year 2020 Capacity Sales Agreements per Year 2020 Capacity Sales Agreements per Year 2020 Segments and Related Information Segment Reporting Disclosure [Text Block] Regulatory Liabilities [Abstract] Regulatory Liabilities [Abstract] Schedule of Regulatory Liabilities [Table] Schedule of Regulatory Liabilities [Table] Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Emission allowances [Member] Emission Allowances [Member] Discloses the amount of regulatory liability arising from emission allowances sales. Asset retirement obligations [Member] Asset Retirement Obligation Costs [Member] Removal Costs [Member] Removal Costs [Member] Deferred Fuel Costs [Member] Deferred Fuel Costs [Member] Pension [Member] Pension Costs [Member] Other Regulatory Assets (Liabilities) [Member] Other Regulatory Assets (Liabilities) [Member] Regulatory Liabilities [Line Items] Regulatory Liabilities [Line Items] Public Utility, Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] Public Utility [Axis] Public Utility [Axis] Utility Plant [Domain] Utility Plant [Domain] Land and other assets not depreciated [Member] Land and other assets not depreciated [Member] Amount of total utility plant comprised of land and other assets that are not depreciated. Energy Plan [Member] Energy Plan [Member] Additional amortization allowed to help maintain cash flows during KCPL's Comprehensive Energy Plan pursuant to orders of the Public Service Commission of the State of Missouri (MPSC) and the State Corporation Commission of the State of Kansas (KCC). Regulation Status [Axis] Regulation Status [Axis] Regulated and Unregulated Operation [Domain] Regulated and Unregulated Operation [Domain] Public Utility, Property, Plant and Equipment [Line Items] Public Utility, Property, Plant and Equipment [Line Items] Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service Depreciation Depreciation Depreciation and amortization Public Utilities, Property, Plant and Equipment, Generation, Useful Life Public Utilities, Property, Plant and Equipment, Generation, Useful Life Public Utilities, Property, Plant and Equipment, Transmission, Useful Life Public Utilities, Property, Plant and Equipment, Transmission, Useful Life Public Utilities, Property, Plant and Equipment, Distribution, Useful Life Public Utilities, Property, Plant and Equipment, Distribution, Useful Life Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life Public Utilities, Property, Plant and Equipment, Other Property Plant and Equipment, Useful Life Public Utilities, Allowance for Funds Used During Construction, Rate Public Utilities, Allowance for Funds Used During Construction, Rate Utility Plant, at original cost Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract] Public Utilities, Property, Plant and Equipment, Generation or Processing Public Utilities, Property, Plant and Equipment, Generation or Processing Public Utilities, Property, Plant and Equipment, Transmission Public Utilities, Property, Plant and Equipment, Transmission Public Utilities, Property, Plant and Equipment, Distribution Public Utilities, Property, Plant and Equipment, Distribution Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment Public Utilities, Property, Plant and Equipment, Plant in Service Valuation and Qualifying Accounts Disclosure [Table] Valuation and Qualifying Accounts Disclosure [Table] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves Type [Axis] Valuation Allowances and Reserves [Domain] Valuation Allowances and Reserves [Domain] Allowance for Doubtful Accounts [Member] Allowance for Doubtful Accounts [Member] Legal Reserve [Member] Legal Reserve [Member] Reserve for Environmental Costs [Member] Reserve for Environmental Costs [Member] Valuation Allowance of Deferred Tax Assets [Member] Valuation Allowance of Deferred Tax Assets [Member] Valuation and Qualifying Accounts Disclosure [Line Items] Valuation and Qualifying Accounts Disclosure [Line Items] Balance at beginning of period Valuation Allowances and Reserves, Balance Additions charged to costs and expenses Valuation Allowances and Reserves, Additions for Charges to Cost and Expense Additions charged to other accounts Valuation Allowances and Reserves, Additions for Charges to Other Accounts Deductions Valuation Allowances and Reserves, Deductions Balance at end of period Schedule of Rent Expense [Table Text Block] Schedule of Rent Expense [Table Text Block] Unrecorded Unconditional Purchase Obligations And Lease Commitments [Table Text Block] Unrecorded Unconditional Purchase Obligations And Lease Commitments [Table Text Block] Tabular disclosure of unconditional purchase obligations and lease commitments that are not recognized as liabilities on the balance sheet. Schedule Of Environmental Capital Expenditures [Table Text Block] Schedule Of Environmental Capital Expenditures [Table Text Block] Tabular disclosure of environmental expenditures (exclusive of Allowance for Funds Used During Construction and property taxes) over the next five years to comply with environmental regulations. Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Cumulative No Par Preferred Stock [Member] Cumulative No Par Preferred Stock [Member] Preferred stock, with no stated par value, upon which unpaid dividends accumulate until paid to shareholders. Classified within stockholders' equity if nonredeemable of redeemable solely at the option of the issuer. Classified within temporary equity if redemption is outside the control of the issuer. 7.00% Mandatory Convertible Preferred Stock, Series B Class of Stock [Line Items] Class of Stock [Line Items] Optional Redemption Percentage of Par Value Optional Redemption Percentage of Par Value The percentage of par value at which the preferred stock may be redeemed at the option of the Company. Cumulative Preferred Stock [Abstract] Cumulative Preferred Stock [Abstract] Cumulative Preferred Stock [Abstract] Preferred Stock, Shares Redeemed PreferredStockSharesRedeemed Preferred Stock, Shares Redeemed Preferred Stock, Redemption Price Per Share, Including Accrued and Unpaid Dividends Preferred Stock Redemption Price Per Share Including Accrued And Unpaid Dividends The price per share at which stock of any entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer. This amount also includes dividends accrued and unpaid. Accrued and Unpaid Preferred Dividends Per Share Accrued And Unpaid Preferred Dividends Amount represents accrued dividends not yet paid Preferred Stock, Redemption Price Per Share Preferred Stock, Redemption Price Per Share Preferred Stock, Shares Outstanding Preferred Stock, Shares Outstanding Preferred Stock, Redemption Date Preferred Stock, Redemption Date Redemption of cumulative preferred stock Mandatory Convertible Preferred Stock [Abstract] Mandatory Convertible Preferred Stock Mandatory Convertible Preferred Stock [Abstract] Preferred Stock, Years to Conversion PreferredStockYearsToConversion Number of years after issuance that mandatory convertible shares will convert to common stock shares Applicable Market Value, Maximum, Series A Applicable Market Value, Maximum Series A If the Applicable Market Value is greater than this amount, the Conversion Rate shall be 29.0855. Applicable Market Value, Maximum, Series B ApplicableMarketValueMaximumSeriesB If the Applicable Market Value is greater than this amount, the Conversion Rate shall be 31.5060 Conversion Rate, if the Applicable Market Value is equal to or greater than $34.38 Conversion Rate1 Series A The Conversion Rate if the Applicable Market Value is equal to or greater than $34.38. Conversion Rate, if the Applicable Market Value is equal to or greater than $31.74 ConversionRate1SeriesB The Conversion Rate if the Applicable Market Value is equal to or greater than $31.74 Applicable Market Value Less Than Maximum Greater Than Minimum Applicable Market Value Less Maximum Greater Than Minimum If the Applicable Market Value is between these amounts, the Conversion Rate shall be $1,000 divided by the Applicable Market Value. Applicable Market Value, Minimum, Series B ApplicableMarketValueMinimumSeriesB If the Applicable Market Value is less than this amount, the Conversion Rate shall be 37.8080 Applicable Market Value, Minimum, Series A Applicable Market Value, Minimum Series A If the Applicable Market Value is less than this amount, the Conversion Rate shall be 34.9026. Conversion Rate, if the Applicable Market Value is less than or equal to $28.65 Conversion Rate 2 Series A The Conversion Rate if the Applicable Market Value is less than or equal to $28.65. Conversion Rate, if the Applicable Market Value is less than or equal to $26.45 ConversionRate2SeriesB The Conversion Rate if the Applicable Market Value is less than or equal to $26.45 Conversion Rate, Numerator, Series A Conversion Rate Numerator, Series A Amount to be divided by the Applicable Market Value if the Applicable Market Value is less than $34.38 but greater than $28.65. Conversion Rate, Numerator, Series B ConversionRateNumeratorSeriesB Amount to be divided by the Applicable Market Value if the Applicable Market Value is less than $31.74 but greater than $26.45. Conversion Rate, Voluntary Conversion Rate, Voluntary The voluntary conversion rate that mandatory convertible preferred stock can be converted into Great Plains Energy common stock at any time. Preferred Stock, Voting Rights Preferred Stock, Voting Rights Depositary Shares, Liquidation Preference Per Share DepositaryShareLiquidationPreference The per share liquidation preference for depositary shares (representing 1/20th of a share of 7.00% Mandatory Convertible Preferred Stock, Series B) Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule of Finite-Lived Intangible Assets [Table Text Block] Amortization Expense Related to Intangible Assets [Table Text Block] Finite-lived Intangible Assets Amortization Expense [Table Text Block] Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Equity Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Goodwill [Abstract] Goodwill [Abstract] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Goodwill Long-Term Debt Fair Value [Abstract] Long-Term Debt Fair Value [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Reported Value Measurement [Member] Estimate of Fair Value Measurement [Member] Estimate of Fair Value Measurement [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair value of financial instruments [Abstract] Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Long-term Debt Long-term Debt Long-term debt fair value Long-term Debt, Fair Value Regulatory Assets [Abstract] Regulatory Assets [Abstract] Schedule of Regulatory Assets [Table] Schedule of Regulatory Assets [Table] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Taxes recoverable through future rates [Member] Deferred Income Tax Charge [Member] Loss on reacquired debt [Member] Loss on Reacquired Debt [Member] Asset Retirement Obligation Costs [Member] Pension and post-retirement costs [Member] Pension and Other Postretirement Plans Costs [Member] Deferred customer programs [Member] Deferred Customer Programs [Member] Discloses the amount of regulatory asset arising from deferred customer program. Rate case expenses [Member] Rate Case Expenses [Member] Expenses, associated with various rate cases, which are deferred as regulatory assets based on the expected ability to recover them in future rates. This amount is not included in rate base and amortized over various periods. Fuel recovery mechanisms [Member] Acquisition transition costs [Member] Deferred Project Costs [Member] Derivative instruments [Member] Deferred Derivative Gain (Loss) [Member] Iatan No. 1 and Common facilities depreciation and carrying costs [Member] Iatan No1 And Common Facilities Depreciation And Carrying Costs [Member] Discloses the amount of regulatory asset arising from Iatan No. 1 and common facilities depreciation and carrying costs not included in rate base. Iatan No. 2 construction accounting costs [Member] Iatan No2 Construction Accounting Costs [Member] Discloses the amount of regulatory asset arising from Iatan No. 2 operating costs, depreciation expense and carrying costs offset by Iatan No. 2's system energy value not included in rate base. Kansas property tax surcharge [Member] Kansas Property Tax Surcharge [Member] Discloses the amount of regulatory asset arising from the Kansas property tax surcharge not included in rate base and amortized over various periods. Solar Rebates [Member] Renewable Energy Program [Member] Transmission Delivery Charge [Member] Transmission Delivery Charge [Member] Transmission Delivery Charge [Member] LaCygne Deferred Depreciation [Member] LaCygne Deferred Depreciation [Member] Discloses the amount of regulatory asset arising from LaCygne depreciation not included in rate base. Voluntary Separation Program [Member] Voluntary Separation Program [Member] Regulatory asset arising from costs related to the voluntary separation program. Regulatory Assets [Line Items] Regulatory Assets [Line Items] Regulatory Assets, Noncurrent Amount not included in rate base Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided Regulatory Noncurrent Asset, End Date for Recovery Regulatory Noncurrent Asset, End Date for Recovery Common Shareholders' Equity [Line Items] Common Shareholders' Equity [Line Items] Common Shareholders' Equity [Line Items] Common Stock Shares Authorized Prior to Amended Articles of Incorporation CommonStockSharesAuthorizedPriorToAmendedArticlesOfIncorporation Amount of authorized shares permitted to be issued by Great Plains Energy's Articles of Incorporation prior to the Articles being amended in September 2016. Shares authorized under the Dividend Reinvestment and Direct Stock Purchase Plan (in shares) Dividend reinvestment and direct stock purchase plan number of shares registered The number of shares registered with the Securities and Exchange Commission for the Dividend Reinvestment and Direct Stock Purchase Plan. Number of shares available for grant under the Dividend Reinvestment and Direct Stock Purchase Plan (in shares) Dividend reinvestment and direct stock purchase plan number of shares available for issuance The difference between the maximum number of shares registered for issuance under the Dividend Reinvestment and Direct Stock Purchase Plan (including the effects of amendments and adjustments), and the number of shares already issued. Shares registered under the defined contribution savings plan (in shares) Defined contribution savings plan number of shares registered The number of shares registered with the Securities and Exchange Commission for the defined contribution savings plan. Number of shares available under the defined contribution savings plan (in shares) Defined contribution plan number of shares available The difference between the maximum number of shares authorized for issuance under the defined contribution plan (including the effects of amendments and adjustments), and the number of shares already issued. Restrictions on the payment of common stock dividends Other Restrictions on Payment of Dividends Restricted net assets of subsidiaries Amount of Restricted Net Assets for Consolidated and Unconsolidated Subsidiaries Dividends Declared [Abstract] Dividends Payable, Amount Per Share Dividends Payable, Amount Per Share Dividends Payable, Date to be Paid Dividends Payable, Date to be Paid Dividends Payable, Date of Record Dividends Payable, Date of Record Dividends Payable, Date Declared, Month and Year Dividends Payable, Date Declared, Month and Year Amortization of: Amortization [Abstract] Nuclear fuel Amortization of Nuclear fuel The noncash expense, not otherwise specified in the taxonomy, charged against earnings in the period to allocate the cost of nuclear fuel over the operating cycle of the nuclear plant. Other Amortization of Other Deferred Charges Investment tax credit amortization Income from equity investments, net of income taxes Other operating activities (Note 3) Total Other Operating Activities Total increase (decrease) in operating capital plus other cash or noncash adjustments to reconcile net income to cash provided by (used in) operating activities. Net cash from operating activities Utility capital expenditures Allowance for borrowed funds used during construction Allowance For Borrowed Funds Used During Construction The component of the allowance for funds used during construction during the period based on the interest rate on borrowed funds used in financing the construction of regulated assets. Purchases of nuclear decommissioning trust investments Payments to Acquire Investments to be Held in Decommissioning Trust Fund Proceeds from nuclear decommissioning trust investments Proceeds from Decommissioning Trust Fund Assets Net money pool lending Payments for (Proceeds from) Money Pool Lending The net cash (inflows) or outflows in money pool lending. Proceeds from sale of transmission assets Proceeds from Sale of Property, Plant, and Equipment Other investing activities Net cash from investing activities Proceeds from issuance of long-term debt from remarketing Proceeds From Issuance Of Long-Term Debt From Remarketing Proceeds from issuance of long-term debt from remarketing of EIRR Bonds. Repayment of long-term debt from remarketing Repayment Of Long-Term Debt From Remarketing Repayment of long-term debt from remarketing of EIRR Bonds Issuance fees Payments of Debt Issuance Costs Repayment of long-term debt Net change in collateralized short-term borrowings Proceeds from (Repayments of) Other Debt Net money pool borrowings ProceedsFrom(RepaymentsOf)MoneyPoolBorrowings The net cash inflows or (outflows) in money pool borrowings. Net cash from financing activities Net Change in Cash and Cash Equivalents Electric Revenues [Member] Electric Revenues [Member] The aggregate revenue, whether regulated or unregulated, derived from the generation, transmission and distribution of electricity. Fuel And Purchased Power Expense [Member] FuelAndPurchasedPowerExpense [Member] Fuel costs incurred that are directly related to goods produced and sold during the reporting period, and the amount of operating expense for purchased power of regulated operation. Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Regulatory Asset [Member] Regulatory Asset [Member] Capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. Regulatory Liability [Member] Regulatory Liability [Member] The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period. Gains (losses) reflected in the income statement for changes in fair value of commodity contracts not designated as hedging Derivative, Gain (Loss) on Derivative, Net Amount of gain (loss) recognized in regulatory account for changes in fair value of commodity contracts not designated as hedging Derivative Instruments Gain Loss Recognized In Regulatory Account On Derivatives Gains and losses (net) on derivative instruments that were recognized in a regulatory account during the current period. Gains (losses) reflected in the income statement or regulatory account for changes in fair value of commodity contracts not designated as hedging DerivativeInstrumentsGainLossRecognizedInIncomeOrRegulatoryAccount Amount of increase (decrease) in the fair value of derivatives recognized in the income statement or a regulatory asset/liability. Cash Flow Hedge Loss to be Reclassified within Twelve Months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Maximum number of shares of common shares authorized (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Equity compensation expense Allocated Share-based Compensation Expense Income tax benefit Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Expected volatility (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected volatility, minimum (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Expected volatility, maximum (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum Expected dividend yield (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Risk-free interest rate (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Risk-free interest rate, minimum (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Risk-free interest rate, maximum (in hundredths) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Earned (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Earned in Period The number of equity-based payment instruments, excluding stock (or unit) options, that were earned during the reporting period. Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Performance adjustment (in shares) Share-based Compensation Arrangement by Share-based payment Award, Equity Instruments Other than Options, Performance adjustment The number of equity-based payment instruments, excluding stock (or unit) options, that were adjusted during the reporting period based on performance criteria. Ending balance (in shares) Weighted average beginning balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Weighted average granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted average vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Weighted average earned (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Earned in period, weighted average grant date fair value The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee earned the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. Weighted average forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Weighted average performance adjustment (in dollars per share) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Performance Adjustments Weighted Average Grant Date Fair Value Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were adjusted during the reporting period based on performance criteria. Weighted average ending balance (in dollars per share) Total unrecognized compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Total fair value of shares vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Remaining weighted-average contractual term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms Fair value of performance shares earned and paid Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Earned And Paid Total Fair Value The total fair value of equity-based awards for which the grantee earned and was paid during the reporting period by satisfying service and performance requirements. Jointly Owned Electric Utility Plants [Text Block] Jointly Owned Electric Utility Plants [Text Block] The entire disclosure on jointly owned electric utility plants. Condensed Financial Information of Parent Company Only Disclosure [Abstract] Condensed Financial Statements [Table] Condensed Financial Statements [Table] Condensed Financial Information of Parent Company Only Disclosure [Text Block] Condensed Financial Information of Parent Company Only Disclosure [Text Block] Receivables Increase (Decrease) in Accounts Receivable Accounts receivable pledged as collateral Increase decrease in accounts receivable pledged as collateral The increase (decrease) during the reporting period in the amount due within one year (or one business cycle) from customers for the credit sale of goods and services where those amounts have been pledged as collateral. Fuel inventories Increase (Decrease) in Fuel Inventories Materials and supplies Increase (Decrease) in Raw Materials, Packaging Materials and Supplies Inventories Accounts payable Increase (Decrease) in Accounts Payable Deferred refueling outage costs Increase Decrease In Deferred Refueling Outage Costs The increase (decrease) in deferred refueling outage costs. Pension and post-retirement benefit obligations Increase (Decrease) in Pension and Postretirement Obligations Allowance for equity funds used during construction Increase (Decrease) in Allowance for Equity Funds Used During Construction Fuel recovery mechanisms Increase (Decrease) in over (under) Energy Recovery Solar rebates paid SolarRebatesPaid The amount of cash paid to customers during the current period for solar rebates. Total other operating activities Cash paid during the period: Supplemental Cash Flow Information [Abstract] Interest Interest Paid, Net Income taxes Income Taxes Paid Non-cash investing activities: Other Noncash Investing and Financing Items [Abstract] Liabilities accrued for capital expenditures Construction in Progress Expenditures Incurred but Not yet Paid Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Summary of Significant Accounting Policies [Text Block] Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Wolf Creek Unit [Member] Wolf Creek Unit [Member] Information on the Wolf Creek jointly owned nuclear utility plant. Other Utility Plants [Member] Other Utility Plants [Member] Other utility plants owned by the entity. Asset Retirement Obligations, Description Asset Retirement Obligations, Description Increase in asset retirement obligations due to CCR regulations IncreaseInAssetRetirementObligationsDueToCCRRegulations Total increase in asset retirement obligations (ARO's) due to Coal Combustion Residual (CCR) regulations enacted by the EPA. The increase includes both newly created ARO's and revisions to existing ARO's Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset Retirement Obligation, Roll Forward Analysis [Roll Forward] Asset Retirement Obligation, Beginning Balance Asset Retirement Obligation Additions Asset Retirement Obligation, Liabilities Incurred Revision in timing and/or estimates Asset Retirement Obligation, Revision of Estimate Settlements Asset Retirement Obligation, Liabilities Settled Accretion Asset Retirement Obligation, Accretion Expense Asset Retirement Obligation, Ending Balance Asset Retirement Obligations, Liability Not Recognized Asset Retirement Obligations, Liability Not Recognized Fair Value Measurements Fair Value Disclosures [Text Block] Income Statement [Abstract] Operating Revenues Electric Revenue [Abstract] Electric revenues Operating Expenses Costs and Expenses [Abstract] Fuel and purchased power FuelAndPurchasedPower Amount of operating expense for fuel and purchased power used by regulated operation Transmission Cost of Transmission Utility operating and maintenance expenses Costs to achieve the anticipated acquisition of Westar Energy, Inc. Business Combination, Acquisition Related Costs General taxes Taxes, Miscellaneous Other Total Costs and Expenses Operating income Non-operating income Nonoperating income Includes equity component of Allowance for Funds Used During Construction and the aggregate amount of other income amounts resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) profits on securities (net of losses), and (d) miscellaneous other income items. Non-operating expenses Other Nonoperating Expense Income before income tax expense and income from equity investments Income tax expense Income from equity investments, net of income taxes Net income Preferred stock dividend requirements and redemption premium Preferred Stock Dividends, Income Statement Impact Earnings available for common shareholders Net Income (Loss) Available to Common Stockholders, Basic Average number of basic common shares outstanding Weighted Average Number of Shares Outstanding, Basic Average number of diluted common shares outstanding Weighted Average Number of Shares Outstanding, Diluted Basic earnings per common share Diluted earnings per common share Comprehensive Income Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Other comprehensive income Other Comprehensive Income (Loss), Net of Tax [Abstract] Gain (loss) on derivative hedging instruments Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax Income tax benefit (expense) Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax Net gain (loss) on derivative hedging instruments Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Reclassification to expenses, net of tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax Derivative hedging activity, net of tax Net gain (loss) arising during period Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax Income tax (expense) benefit Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax Net gain (loss) arising during period, net of tax Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax Amortization of net losses included in net periodic benefit costs, net of tax Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax Change in unrecognized pension expense, net of tax Total other comprehensive income Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent General and administrative Other General and Administrative Expense Operating Expenses Operating Expenses Equity in earnings (loss) from Subsidiaries Non-operating income Other Nonoperating Income Earnings available for common shareholders Income tax benefit (expense) on derivative hedging instruments Reclassification to expenses Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax Income tax (expense) benefit on reclassification to expenses Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Reclassification to expenses, net of tax Other comprehensive income from subsidiaries, net of tax Other comprehensive income from subsidiaries, net of tax Other comprehensive income from subsidiaries, net of tax Total other comprehensive income Comprehensive income Nuclear Plant Schedule Of Nuclear Plant [Text Block] This element can be used to encapsulate the entire disclosure for plant used in connection with the generation of nuclear energy. Entity information [Abstract] Entity information for DEI Document Information [Table] Document Information [Table] Document Information, Document [Axis] Document Information, Document [Axis] Document [Domain] Document [Domain] Document Information [Line Items] Document Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Quarterly Financial Information [Text Block] Quarterly Financial Information [Text Block] Schedule of Change in Asset Retirement Obligation [Table Text Block] Schedule of Change in Asset Retirement Obligation [Table Text Block] Deferred Income Taxes Disclosure [Abstract] Deferred Income Taxes Disclosure [Abstract] Components of Deferred Tax Assets and Liabilities [Abstract] Components of Deferred Tax Assets and Liabilities [Abstract] Deferred Tax Assets (Liabilities), Net of Valuation Allowance, Current Classification [Abstract] Deferred Tax Assets, Net of Valuation Allowance, Current Classification [Abstract] Net operating loss carryforward, current Deferred tax assets, operating loss carryforwards, current The sum of the tax effects as of the balance sheet date of the amount of excesses of tax deductions over gross income in a year which can be used on the tax returns within the next twelve months to reduce taxable income or income taxes payable in a future year, for which there must be sufficient tax-basis income to utilize a portion or all of the carryforward amount to realize the deferred tax asset. Deferred tax assets (liabilities), other current Deferred Tax Assets (Liabilities), Other, Current The tax effect as of the balance sheet date of the amount of estimated future tax deductions or taxable amounts arising from other temporary differences not otherwise specified in the taxonomy. Deferred tax assets (liabilities), before valuation allowance, current Deferred Tax Assets Liabilities, Before Valuation Allowance, Current Amount of current deferred tax asset attributable to deductible temporary differences and carryforwards, net of current deferred tax liability attributable to taxable temporary differences before allocation of valuation allowances. Valuation allowance, current Deferred Tax Assets, Valuation Allowance, Current Current deferred income tax asset Deferred Tax Assets, Net, Current Deferred Tax Assets (Liabilities), Net of Valuation Allowance, Noncurrent Classification [Abstract] Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Classification [Abstract] Plant related Deferred Tax Liabilities, Property, Plant and Equipment Income taxes on future regulatory recoveries Deferred Tax Liabilities, Regulatory Assets and Liabilities Deferred Tax Assets, Derivative Instruments Deferred Tax Liabilities, Derivative Instruments Deferred Tax Liabilities, Derivatives Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions Deferred Tax Liabilities, Compensation and Benefits, Pensions DeferredTaxLiabilitiesPensionAndPostRetirementBenefits The amount as of the balance sheet date of the estimated future tax effects attributable to pension and post-retirement benefits. SO2 emission allowance sales Deferred tax asset SO2 emission allowance sales The amount as of the balance sheet date of the estimated future tax effects attributable to the sales of SO 2 emission allowances. Fuel recovery mechanisms Deferred tax liabilities fuel recovery mechanisms The amount as of the balance sheet date of the estimated future tax effects attributable to fuel clause adjustments. Transition costs Deferred tax liabilities transition costs The amount as of the balance sheet date of the estimated future tax effects attributable to transition costs. Tax credit carryforwards Deferred Tax Assets, Tax Credit Carryforwards Long-term debt fair value adjustment Deferred Tax Liabilities, Financing Arrangements Customer demand programs Deferred tax liabilities customer demand programs The amount as of the balance sheet date of the estimated future tax effects attributable to customer demand programs. Solar rebates Deferred Tax Liabilities Solar Rebates The amount as of the balance sheet date of the estimated future tax effects attributable to solar rebates paid to customers. Net operating loss carryforward Deferred tax asset, net operating loss carryforward, noncurrent The sum of the tax effects as of the balance sheet date of the amount of excesses of tax deductions over gross income in a year which cannot be used on the tax returns in the current year but can be carried forward to reduce taxable income or income taxes payable in a future year, for which there must be sufficient tax-basis income to utilize a portion or all of the carryforward amount to realize the deferred tax asset. Deferred Tax Assets, Other Deferred Tax Assets, Other Deferred Tax Liabilities, Other Deferred Tax Liabilities, Other Net noncurrent deferred income tax liability before valuation allowance Deferred Tax Assets (Liabilities), Before Valuation Allowance, Noncurrent Amount of noncurrent deferred tax asset attributable to deductible temporary differences and carryforwards, net of noncurrent deferred tax liability attributable to taxable temporary differences before allocation of valuation allowances. Valuation allowance Deferred Tax Assets, Valuation Allowance, Noncurrent Net noncurrent deferred income tax liability Net deferred income tax liability Deferred Tax Liabilities, Net Deferred Tax Assets (Liabilities), Net, Noncurrent Deferred Tax Assets (Liabilities), Net Deferred Tax Assets, Net Deferred Tax Assets (Liabilities), Gross [Abstract] Deferred Tax Assets, Gross [Abstract] Gross deferred income tax assets Deferred Tax Assets, Gross Gross deferred income tax liabilities Deferred Tax Liabilities, Gross Contingencies Disclosure [Text Block] Contingencies Disclosure [Text Block] Loans Notes Trade And Other Receivables Disclosure And Transfers And Servicing Of Financial Asset [Text Block] Loans Notes Trade And Other Receivables Disclosure And Transfers And Servicing Of Financial Asset [Text Block] Includes disclosure of claims held for amounts due a company. Examples include trade accounts receivables, notes receivables, loans receivables. Also provides the disclosures pertaining to a transferor's continuing involvement in financial assets that it has transferred in a securitization or asset-backed financing arrangements. Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Designated as Hedging Instrument [Member] Designated as Hedging Instrument [Member] Current assets [Member] Current assets [Member] Amounts recorded in current assets for open derivative positions or at the time of settlement of a closed position. Current liabilities [Member] Current liabilities [Member] Amounts recorded in current liabilities for open derivative positions or at the time of settlement of a closed position. Noncurrent liabilities [Member] Noncurrent liabilities [Member] Amounts recorded in noncurrent liabilities for open derivatvie positions or at the time of settlement of a closed position. Deferred income taxes [Member] Deferred income taxes [Member] Amounts recorded in deferred income taxes for open derivative positions or at the time of settlement of a closed position. Other Balance Sheet Location [Member] Other Balance Sheet Location [Member] Other current assets, other investments and other assets, other current liabilities or other deferred credits and other liabilities. Derivative Instruments [Member] Derivative Instruments [Member] Current assets - derivative instruments, Investments and other assets - derivative instruments, Current liabilities - derivative instruments, Deferred credits - derivative instruments, Liabilities - derivative instruments. Other/Derivative Instruments Other Balance Sheet And Derivative Instrument Location [Member] Current assets - other or derivative instruments, Investments and other assets - other or derivative instruments, Current liabilities - other or derivative instruments, Deferred credits - other or derivative instruments, Liabilities - other or derivative instruments. Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Goodwill and Intangible Assets [Text Block] Goodwill and Intangible Assets Disclosure [Text Block] Changes in nuclear decommissioning trust fund Changes in nuclear decommissioning trust fund [Table Text Block] A tabular disclosure that summarizes the change in nuclear decommissioning trust fund during the period. Detail of assets held in nuclear decommissioning trust fund Detail of assets held in nuclear decommissioning trust fund [Table Text Block] This item represents the entire disclosure related to nuclear decommissioning trust fund which consist of all investments in certain debt and equity securities (and other assets). The nuclear decommission fund is maintained to pay for the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments and government appropriations. Gains and losses from the sale of securities by the nuclear decommissioning trust fund Nuclear Decomissioning Trust fund Sale of Securities Gains Losses [Table Text Block] This item represents the entire disclosure related to realized gain or loss on sale of securities related to nuclear decommissioning trust fund. Nuclear plant decommissioning costs [Table Text Block] Nuclear Plant Decommissioning Costs [Table Text Block] A tabular disclosure of current and future decommissioning costs related to nuclear plants. Valuation Allowance [Abstract] Valuation Allowance [Table] Valuation Allowance [Table] Valuation Allowance by Deferred Tax Asset [Axis] Valuation Allowance by Deferred Tax Asset [Axis] Deferred Tax Asset [Domain] Deferred Tax Asset [Domain] Valuation Allowance [Line Items] Valuation Allowance [Line Items] Valuation Allowance, Deferred Tax Asset, Change in Amount Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Regulatory (Asset) Liability [Member] Regulatory (Asset) Liability [Member] Regulatory (Asset) Liability Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, by Asset Class [Domain] Non-Operating Income [Member] Non Operating Income [Member] Amount of non-operating income. Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Net asset (liability) at beginning of period Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Regulatory Account Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Regulatory Account Amount of gain (loss) recognized in a regulatory account of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. Sales Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Sales Purchases Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Purchases Settlements Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Settlements Net asset (liability) at end of period Total unrealized gains and (losses) relating to assets and liabilities still on the consolidated balance sheet at period end Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Income [Abstract] Earnings Per Share Reconciliation [Abstract] Less: preferred stock dividend requirements and redemption premium Common Shares Outstanding [Abstract] Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Average number of common shares outstanding (in shares) Add: effect of dilutive securities (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Diluted average number of common shares outstanding (in shares) Earnings Per Share [Abstract] Earnings Per Share [Abstract] Basic and Diluted EPS Schedule of Jointly Owned Utility Plants [Table Text Block] Schedule of Jointly Owned Utility Plants [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Transource Energy, LLC [Member] Transource Energy, LLC [Member] Transource Energy, LLC GPE Transmission Holding Company, LLC [Member] GPE Transmission Holding Company, LLC [Member] GPE Transmission Holding Company, LLC AEP Transmission Holding Company, LLC [Member] AEP Transmission Holding Company, LLC [Member] AEP Transmission Holding Company, LLC Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage Equity Method Investment, Description of Principal Activities Equity Method Investment, Description of Principal Activities Ownership Percentage of Majority Owner Noncontrolling Interest, Ownership Percentage by Parent