Evergy Metro 10-Q 6 Aug 15 2015 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Aug. 03, 2015
Document Information [Line Items]
Entity Registrant Name	Great Plains Energy Inc
Entity Central Index Key	1,143,068
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		154,333,594
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015

Consolidated Statements of Inco

Consolidated Statements of Income and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Operating Revenues
Electric revenues	$ 609	$ 648.4	$ 1,158.1		$ 1,233.5
Operating Expenses
Fuel	99.9	115.4	207.5		250.6
Purchased power	48.8	79.1	94.2		124.5
Transmission	20.3	18.7	41.2		36.3
Utility operating and maintenance expenses	183.4	183.4	354.9		364.1
Depreciation and amortization	83.5	75.6	163.3		150.1
General taxes	52.1	50.6	104.8		103.4
Other General and Administrative Expense	1.1	1.4	2.2		2.4
Costs and Expenses, Total	489.1	524.2	968.1		1,031.4
Operating Income (Loss)	119.9	124.2	190		202.1
Non-operating income	2.2	7	8.2		13.4
Non-operating expenses	(3.6)	(3.9)	(7.3)		(7)
Interest charges	(50)	(48.3)	(97.3)		(97.7)
Income before income tax (expense) benefit and income (loss) from equity investments	68.5	79	93.6		110.8
Income tax (expense) benefit	(24.5)	(27)	(31)		(35.1)
(Income) loss from equity investments, net of income taxes	0.4	0.1	0.7		0.2
Net income (loss)	44.4	52.1	63.3		75.9
Preferred stock dividend requirements	0.4	0.4	0.8		0.8
Earnings (loss) available for common shareholders	$ 44	$ 51.7	$ 62.5		$ 75.1
Average number of common shares outstanding (in shares)	154.1	153.8	154.1		153.8
Average number of diluted common shares outstanding (in shares)	154.5	154	154.5		154
Earnings Per Share, Basic and Diluted [Abstract]
Earnings Per Share, Basic and Diluted	$ 0.28	$ 0.34	$ 0.40		$ 0.49
Comprehensive Income
Net income (loss)	$ 44.4	$ 52.1	$ 63.3		$ 75.9
Other comprehensive income
Reclassification to expenses, net of tax	1.4	2.5	2.8		5.3
Derivative hedging activity, net of tax	1.4	2.5	2.8		5.3
Amortization of net losses included in net periodic benefit costs, net of tax	0.2	0	0.3		0.2
Change in unrecognized pension expense, net of tax	0.2	0	0.3		0.2
Total other comprehensive income (loss)	1.6	2.5	3.1	[1]	5.5	[1]
Comprehensive income (loss)	$ 46	$ 54.6	$ 66.4		$ 81.4
Common Stock, Dividends, Per Share, Declared	$ 0.245	$ 0.23	$ 0.49		$ 0.46
Kansas City Power and Light Company [Member]
Operating Revenues
Electric revenues	$ 417.4	$ 439.5	$ 787.8		$ 830.5
Operating Expenses
Fuel	73.1	88.2	147.9		181.8
Purchased power	28.6	40.5	50.5		59.4
Transmission	12.7	12	26.1		22.6
Utility operating and maintenance expenses	124.6	129.1	242.9		256.3
Depreciation and amortization	59.8	52.6	116.3		104.3
General taxes	39.5	38.9	79.7		80.4
Other General and Administrative Expense	(0.2)	0	(0.2)		0
Costs and Expenses, Total	338.1	361.3	663.2		704.8
Operating Income (Loss)	79.3	78.2	124.6		125.7
Non-operating income	1.3	5.2	5.7		11.2
Non-operating expenses	(2.2)	(2)	(3.9)		(3.6)
Interest charges	(34.1)	(31)	(65.6)		(61.7)
Income before income tax (expense) benefit and income (loss) from equity investments	44.3	50.4	60.8		71.6
Income tax (expense) benefit	(14.9)	(15.6)	(18.2)		(19.6)
Net income (loss)	29.4	34.8	42.6		52
Comprehensive Income
Net income (loss)	29.4	34.8	42.6		52
Other comprehensive income
Reclassification to expenses, net of tax	1.3	1.4	2.7		2.7
Derivative hedging activity, net of tax	1.3	1.4	2.7		2.7
Total other comprehensive income (loss)	1.3	1.4	2.7		2.7
Comprehensive income (loss)	$ 30.7	$ 36.2	$ 45.3		$ 54.7
[1]	Net of tax

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Current Assets
Cash and cash equivalents		$ 12.2	$ 13
Funds on deposit		2.9	1.2
Receivables, net		196.2	160.3
Accounts receivable pledged as collateral		163	171
Fuel inventories, at average cost		102.3	90.1
Materials and supplies, at average cost		152.4	152.7
Deferred refueling outage costs		30.2	12.5
Refundable income taxes		3.4	3.1
Deferred income taxes		89.9	78.1
Prepaid expenses and other assets		35.6	36.9
Assets, Current, Total		788.1	718.9
Utility Plant, at Original Cost
Electric		13,017	12,128.7
Less-accumulated depreciation		4,847	4,828.3
Net utility plant in service		8,170	7,300.4
Construction work in progress		296.8	900
Nuclear Fuel, Net of Amortization		71.1	79.2
Public Utilities, Property, Plant and Equipment, Net		8,537.9	8,279.6
Investments and Other Assets
Nuclear decommissioning trust fund		203.3	199
Regulatory Assets		986.1	1,034.6
Goodwill		169	169
Other Assets, Noncurrent		77.8	74.6
Investments and Other Assets, Total		1,436.2	1,477.2
Assets, Total		10,762.2	10,475.7
Current Liabilities
Notes payable		11	4
Collateralized note payable		163	171
Commercial paper		629.3	358.3
Current maturities of long-term debt		1.1	15.1
Accounts payable		255.8	388
Accrued taxes		78	30.4
Accrued interest		40	41.3
Accrued compensation and benefits		38.9	35.2
Pension and post-retirement liability		2.8	2.8
Other Liabilities, Current		28.8	24.7
Liabilities, Current, Total		1,248.7	1,070.8
Deferred Credits and Other Liabilities
Deferred income taxes		1,132.9	1,089.7
Deferred tax credits		125.3	126
Asset retirement obligations		271.5	195.9
Pension and post-retirement liability		505.9	508.6
Regulatory liabilities		290.7	282.7
Other Liabilities, Noncurrent		81.7	88.9
Liabilities, Noncurrent, Total		2,408	2,291.8
Common shareholders' equity
Common Stock, Value, Issued		2,643.7	2,639.3
Retained earnings		954.2	967.8
Treasury Stock, Value		(2.5)	(2.3)
Accumulated other comprehensive loss	[1]	(15.6)	(18.7)
Common Shareholders' Equity, Total		3,579.8	3,586.1
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued		39	39
Long-term debt		3,486.7	3,488
Total Capitalization		$ 7,105.5	$ 7,113.1
Commitments and Contingencies
Liabilities and Equity, Total		$ 10,762.2	$ 10,475.7
Preferred Stock 3 Point 80 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued		10	10
Preferred Stock 4 Point 50 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued		10	10
Preferred Stock 4 Point 20 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued		7	7
Preferred Stock 4 Point 35 [Member]
Cumulative preferred stock $100 par value
Preferred Stock, Value, Issued		12	12
Kansas City Power and Light Company [Member]
Current Assets
Cash and cash equivalents		2.9	2.7
Funds on deposit		1	0.6
Receivables, net		144.9	128.9
Related party receivables		54.1	68.8
Accounts receivable pledged as collateral		110	110
Fuel inventories, at average cost		70.7	58.8
Materials and supplies, at average cost		110	110.1
Deferred refueling outage costs		30.2	12.5
Refundable income taxes		0	57.5
Deferred income taxes		1	5
Prepaid expenses and other assets		31.5	32.7
Assets, Current, Total		556.3	587.6
Utility Plant, at Original Cost
Electric		9,532.6	8,737.3
Less-accumulated depreciation		3,645.5	3,658.7
Net utility plant in service		5,887.1	5,078.6
Construction work in progress		204.4	791.2
Nuclear Fuel, Net of Amortization		71.1	79.2
Public Utilities, Property, Plant and Equipment, Net		6,162.6	5,949
Investments and Other Assets
Nuclear decommissioning trust fund		203.3	199
Regulatory Assets		726.1	745.7
Other Assets, Noncurrent		30	29.5
Investments and Other Assets, Total		959.4	974.2
Assets, Total		7,678.3	7,510.8
Current Liabilities
Collateralized note payable		110	110
Commercial paper		484	358.3
Current maturities of long-term debt		0	14
Accounts payable		215.3	305.2
Related party payables		0	12.6
Accrued taxes		60.5	23.6
Accrued interest		27.5	29
Accrued compensation and benefits		38.9	35.2
Pension and post-retirement liability		1.5	1.5
Other Liabilities, Current		12.5	12.4
Liabilities, Current, Total		950.2	901.8
Deferred Credits and Other Liabilities
Deferred income taxes		1,033	1,016.9
Deferred tax credits		123.8	124.3
Asset retirement obligations		234.6	177.7
Pension and post-retirement liability		483	485.4
Regulatory liabilities		173.7	172
Other Liabilities, Noncurrent		61.1	59.2
Liabilities, Noncurrent, Total		2,109.2	2,035.5
Common shareholders' equity
Common Stock, Value, Issued		1,563.1	1,563.1
Retained earnings		769.4	726.8
Accumulated other comprehensive loss		(12.2)	(14.9)
Common Shareholders' Equity, Total		2,320.3	2,275
Cumulative preferred stock $100 par value
Long-term debt		2,298.6	2,298.5
Total Capitalization		$ 4,618.9	$ 4,573.5
Commitments and Contingencies
Liabilities and Equity, Total		$ 7,678.3	$ 7,510.8
[1]	Net of tax

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Utility Plant, at Original Cost
Nuclear fuel, amortization	$ 175.7	$ 187.5
Common shareholder's equity
Common stock - shares authorized (in shares)	250,000,000	250,000,000
Common stock-shares issued (in shares)	154,422,890	154,254,037
Treasury stock- shares (in shares)	96,463	91,281
Preferred Stock 3 Point 80 [Member]
Cumulative preferred stock
Cumulative preferred stock par value (in dollars per share)	$ 100	$ 100
Cumulative preferred stock, Shares issued (in share)	100,000	100,000
Preferred Stock, Dividend Rate, Percentage	3.80%	3.80%
Preferred Stock 4 Point 50 [Member]
Cumulative preferred stock
Cumulative preferred stock par value (in dollars per share)	$ 100	$ 100
Cumulative preferred stock, Shares issued (in share)	100,000	100,000
Preferred Stock, Dividend Rate, Percentage	4.50%	4.50%
Preferred Stock 4 Point 20 [Member]
Cumulative preferred stock
Cumulative preferred stock par value (in dollars per share)	$ 100	$ 100
Cumulative preferred stock, Shares issued (in share)	70,000	70,000
Preferred Stock, Dividend Rate, Percentage	4.20%	4.20%
Preferred Stock 4 Point 35 [Member]
Cumulative preferred stock
Cumulative preferred stock par value (in dollars per share)	$ 100	$ 100
Cumulative preferred stock, Shares issued (in share)	120,000	120,000
Preferred Stock, Dividend Rate, Percentage	4.35%	4.35%
Kansas City Power and Light Company [Member]
Utility Plant, at Original Cost
Nuclear fuel, amortization	$ 175.7	$ 187.5
Common shareholder's equity
Common stock - shares authorized (in shares)	1,000	1,000
Common stock-shares issued (in shares)	1	1

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014
Cash Flows from Operating Activities
Net income (loss)	$ 63.3		$ 75.9
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	163.3		150.1
Amortization of:
Nuclear fuel	10		10.3
Other	23.6		26.1
Deferred income taxes, net	31.3		38.4
Investment tax credit amortization	(0.7)		(0.8)
(Income) loss from equity investments, net of income taxes	(0.7)		(0.2)
Other operating activities	(73.4)		(127.9)
Net cash from operating activities	216.7		171.9
Cash Flows from Investing Activities
Utility capital expenditures	(366.8)	[1]	(352.9)
Allowance for borrowed funds used during construction	(3.6)		(6.9)
Purchases of nuclear decommissioning trust investments	(22.3)		(13.9)
Proceeds from nuclear decommissioning trust investments	20.7		12.3
Proceeds from sale of transmission assets	0		37.7
Other investing activities	(24.6)		(17.2)
Net cash from investing activities	(396.6)		(340.9)
Cash Flows from Financing Activities
Issuance of common stock	1.6		2.5
Repayment of long-term debt	(15.1)		(13.4)
Net change in short-term borrowings	278		259.3
Net change in collateralized short-term borrowings	(8)		(4)
Dividends paid	(76.4)		(71.6)
Other financing activities	(1)		(1.9)
Net cash from financing activities	179.1		170.9
Net Change in Cash and Cash Equivalents	(0.8)		1.9
Cash and Cash Equivalents at Beginning of Year	13		10.6
Cash and Cash Equivalents at End of Period	12.2		12.5
Kansas City Power and Light Company [Member]
Cash Flows from Operating Activities
Net income (loss)	42.6		52
Adjustments to reconcile income to net cash from operating activities:
Depreciation and amortization	116.3		104.3
Amortization of:
Nuclear fuel	10		10.3
Other	14.1		15.5
Deferred income taxes, net	20.6		19.2
Investment tax credit amortization	(0.5)		(0.5)
Other operating activities	14.9		(53.2)
Net cash from operating activities	218		147.6
Cash Flows from Investing Activities
Utility capital expenditures	(297.4)		(293.4)
Allowance for borrowed funds used during construction	(2.5)		(6)
Purchases of nuclear decommissioning trust investments	(22.3)		(13.9)
Proceeds from nuclear decommissioning trust investments	20.7		12.3
Proceeds from sale of transmission assets	0		4.7
Other investing activities	(15.4)		(9.5)
Net cash from investing activities	(316.9)		(305.8)
Cash Flows from Financing Activities
Repayment of long-term debt	(14)		0
Net change in short-term borrowings	125.7		195.1
Net money pool borrowings	(12.6)		(0.2)
Dividends paid	0		(36)
Net cash from financing activities	99.1		158.9
Net Change in Cash and Cash Equivalents	0.2		0.7
Cash and Cash Equivalents at Beginning of Year	2.7		4
Cash and Cash Equivalents at End of Period	$ 2.9		$ 4.7
[1]	Capital expenditures reflect year to date amounts for the periods presented.

Consolidated Statements of Comm

Consolidated Statements of Common Shareholders' Equity - USD ($) $ in Millions	Total	Kansas City Power and Light Company [Member]	Common Stock [Member]	Common Stock [Member]Kansas City Power and Light Company [Member]	Retained Earnings [Member]	Retained Earnings [Member]Kansas City Power and Light Company [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]Kansas City Power and Light Company [Member]
Beginning balance at Dec. 31, 2013			$ 2,631.1	$ 1,563.1	$ 871.4	$ 636.4	$ (2.8)	$ (25.3)	$ (20.2)
Beginning balance (in shares) at Dec. 31, 2013			153,995,621	1
Beginning balance, treasury stock (in shares) at Dec. 31, 2013							(129,290)
Issuance of common stock			$ 2.4
Issuance of common stock (in shares)			95,745
Issuance of restricted common stock			$ 1.9
Issuance of restricted common stock (in shares)			71,860
Equity compensation expense, net of forfeitures			$ 0.2
Unearned Compensation [Abstract]
Issuance of restricted common stock			(1.9)
Compensation expense recognized			1
Stockholders' Equity, Other			1.1
Net income (loss)	$ 75.9	$ 52			75.9	52
Dividends:
Common stock					(70.8)	(36)
Preferred stock - at required rates					(0.8)
Performance shares					(0.4)
Treasury shares acquired							$ (1.9)
Treasury shares acquired (in shares)							(73,273)
Treasury shares reissued							$ 2.4
Treasury shares reissued (in shares)							112,369
Derivative hedging activity, net of tax	5.3	2.7						5.3	2.7
Change in unrecognized pension expense, net of tax	0.2							0.2
Ending balance at Jun. 30, 2014	3,489	2,198	$ 2,635.8	$ 1,563.1	875.3	652.4	$ (2.3)	(19.8)	(17.5)
Ending balance, treasury stock (in shares) at Jun. 30, 2014							(90,194)
Ending balance (in shares) at Jun. 30, 2014			154,163,226	1
Beginning balance at Dec. 31, 2014	$ 3,586.1	2,275	$ 2,639.3	$ 1,563.1	967.8	726.8	$ (2.3)	(18.7)	(14.9)
Beginning balance (in shares) at Dec. 31, 2014			154,254,037	1
Beginning balance, treasury stock (in shares) at Dec. 31, 2014	(91,281)						(91,281)
Issuance of common stock			$ 2.4
Issuance of common stock (in shares)			90,916
Issuance of restricted common stock			$ 2
Issuance of restricted common stock (in shares)			77,937
Equity compensation expense, net of forfeitures			$ 0.9
Unearned Compensation [Abstract]
Issuance of restricted common stock			(2)
Compensation expense recognized			1
Stockholders' Equity, Other			0.1
Net income (loss)	$ 63.3	42.6			63.3	42.6
Dividends:
Common stock					(75.6)	0
Preferred stock - at required rates					(0.8)
Performance shares					(0.5)
Treasury shares acquired							$ (1.4)
Treasury shares acquired (in shares)							(53,895)
Treasury shares reissued							$ 1.2
Treasury shares reissued (in shares)							48,713
Derivative hedging activity, net of tax	2.8	2.7						2.8	2.7
Change in unrecognized pension expense, net of tax	0.3							0.3
Ending balance at Jun. 30, 2015	$ 3,579.8	$ 2,320.3	$ 2,643.7	$ 1,563.1	$ 954.2	$ 769.4	$ (2.5)	$ (15.6)	$ (12.2)
Ending balance, treasury stock (in shares) at Jun. 30, 2015	(96,463)						(96,463)
Ending balance (in shares) at Jun. 30, 2015			154,422,890	1

Consolidated Statements of Com7

Consolidated Statements of Common Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Stock Transactions, Parenthetical Disclosures [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 0.245	$ 0.23	$ 0.49	$ 0.46

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies [Text Block]	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization Great Plains Energy, a Missouri corporation incorporated in 2001, is a public utility holding company and does not own or operate any significant assets other than the stock of its subsidiaries. Great Plains Energy's wholly owned direct subsidiaries with significant operations are as follows: • KCP&L is an integrated, regulated electric utility that provides electricity to customers primarily in the states of Missouri and Kansas. KCP&L has one active wholly owned subsidiary, Kansas City Power & Light Receivables Company (KCP&L Receivables Company). • KCP&L Greater Missouri Operations Company (GMO) is an integrated, regulated electric utility that provides electricity to customers in the state of Missouri. GMO also provides regulated steam service to certain customers in the St. Joseph, Missouri area. GMO has two active wholly owned subsidiaries, GMO Receivables Company and MPS Merchant Services, Inc. (MPS Merchant). MPS Merchant has certain long-term natural gas contracts remaining from its former non-regulated trading operations. Great Plains Energy also wholly owns GPE Transmission Holding Company, LLC (GPETHC). GPETHC owns 13.5% of Transource Energy, LLC (Transource) with the remaining 86.5% owned by AEP Transmission Holding Company, LLC (AEPTHC), a subsidiary of American Electric Power Company, Inc. GPETHC accounts for its investment in Transource under the equity method. Transource is focused on the development of competitive electric transmission projects. Each of Great Plains Energy's and KCP&L's consolidated financial statements includes the accounts of their subsidiaries. Intercompany transactions have been eliminated. Great Plains Energy's sole reportable business segment is electric utility. See Note 18 for additional information. Basic and Diluted Earnings per Common Share Calculation To determine basic earnings per common share (EPS), preferred stock dividend requirements are deducted from net income before dividing by the average number of common shares outstanding. The effect of dilutive securities, calculated using the treasury stock method, assumes the issuance of common shares applicable to performance shares and restricted stock. The following table reconciles Great Plains Energy's basic and diluted EPS. Three Months Ended Year to Date 2015 2014 2015 2014 Income (millions, except per share amounts) Net income $ 44.4 $ 52.1 $ 63.3 $ 75.9 Less: preferred stock dividend requirements 0.4 0.4 0.8 0.8 Earnings available for common shareholders $ 44.0 $ 51.7 $ 62.5 $ 75.1 Common Shares Outstanding Average number of common shares outstanding 154.1 153.8 154.1 153.8 Add: effect of dilutive securities 0.4 0.2 0.4 0.2 Diluted average number of common shares outstanding 154.5 154.0 154.5 154.0 Basic and diluted EPS $ 0.28 $ 0.34 $ 0.40 $ 0.49 Anti-dilutive shares excluded from the computation of diluted EPS are detailed in the following table. Three Months Ended Year to Date 2015 2014 2015 2014 Performance shares — 475,549 — 475,549 Restricted stock shares — — — 287 Dividends Declared In August 2015 , Great Plains Energy's Board of Directors (Board) declared a quarterly dividend of $0.245 per share on Great Plains Energy's common stock. The common dividend is payable September 21, 2015 , to shareholders of record as of August 28, 2015 . The Board also declared regular dividends on Great Plains Energy's preferred stock, payable December 1, 2015 , to shareholders of record as of November 6, 2015 . New Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in Generally Accepted Accounting Principles (GAAP) when it becomes effective. In July 2015, the FASB approved a one year deferral of the effective date of ASU No. 2014-09. A final ASU formally amending the effective date of ASU No. 2014-09 from January 1, 2017, to January 1, 2018, is expected to be issued in the third quarter of 2015. The standard permits the use of either the retrospective or cumulative effect transition method. The Companies are evaluating the effect that ASU No. 2014-09 will have on their consolidated financial statements and related disclosures. The Companies have not yet selected a transition method nor have they determined the effect of the standard on their ongoing financial reporting. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs , which requires that debt issuance costs related to a recognized debt liability be presented on the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. Great Plains Energy and KCP&L currently include debt issuance costs in Other - Investments and Other Assets on their consolidated balance sheets. The new guidance is to be applied retrospectively and is effective for interim and annual periods beginning after December 15, 2015, with early adoption permitted. The Companies intend to early adopt ASU No. 2015-03 for the 2015 Form 10-K.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	6 Months Ended
	Jun. 30, 2015
Supplemental Cash Flow Elements [Abstract]
Cash Flow, Supplemental Disclosures [Text Block]	2. SUPPLEMENTAL CASH FLOW INFORMATION Great Plains Energy Other Operating Activities Year to Date June 30 2015 2014 Cash flows affected by changes in: (millions) Receivables $ (36.0 ) $ (57.1 ) Accounts receivable pledged as collateral 8.0 4.0 Fuel inventories (12.2 ) 3.9 Materials and supplies 0.3 4.1 Accounts payable (108.2 ) (76.1 ) Accrued taxes 47.5 46.0 Accrued interest (1.3 ) (1.3 ) Deferred refueling outage costs (17.7 ) 8.4 Pension and post-retirement benefit obligations 25.0 5.3 Allowance for equity funds used during construction (3.5 ) (9.0 ) Fuel recovery mechanism 25.6 (17.3 ) Solar rebates paid (4.8 ) (33.3 ) Other 3.9 (5.5 ) Total other operating activities $ (73.4 ) $ (127.9 ) Cash paid during the period: Interest $ 91.9 $ 88.2 Income taxes $ 0.2 $ 0.1 Non-cash investing activities: Liabilities accrued for capital expenditures $ 34.8 $ 46.7 KCP&L Other Operating Activities Year to Date June 30 2015 2014 Cash flows affected by changes in: (millions) Receivables $ (1.4 ) $ (34.4 ) Fuel inventories (11.9 ) 6.6 Materials and supplies 0.1 2.8 Accounts payable (69.7 ) (38.8 ) Accrued taxes 94.4 31.9 Accrued interest (1.5 ) (1.5 ) Deferred refueling outage costs (17.7 ) 8.4 Pension and post-retirement benefit obligations 25.1 4.4 Allowance for equity funds used during construction (2.7 ) (8.5 ) Fuel recovery mechanism 0.6 2.4 Solar rebates paid (4.1 ) (10.7 ) Other 3.7 (15.8 ) Total other operating activities $ 14.9 $ (53.2 ) Cash paid during the period: Interest $ 61.2 $ 57.2 Non-cash investing activities: Liabilities accrued for capital expenditures $ 31.4 $ 39.3

Receivables

Receivables	6 Months Ended
	Jun. 30, 2015
Receivables [Abstract]
Loans Notes Trade And Other Receivables Disclosure And Transfers And Servicing Of Financial Asset [Text Block]	3. RECEIVABLES Great Plains Energy's and KCP&L's receivables are detailed in the following table. June 30 December 31 2015 2014 Great Plains Energy (millions) Customer accounts receivable - billed $ 3.2 $ 1.1 Customer accounts receivable - unbilled 123.2 75.3 Allowance for doubtful accounts - customer accounts receivable (5.3 ) (2.8 ) Other receivables 75.1 86.7 Total $ 196.2 $ 160.3 KCP&L Customer accounts receivable - billed $ 1.1 $ 0.6 Customer accounts receivable - unbilled 77.3 49.7 Allowance for doubtful accounts - customer accounts receivable (2.8 ) (1.2 ) Other receivables 69.3 79.8 Total $ 144.9 $ 128.9 Great Plains Energy's and KCP&L's other receivables at June 30, 2015 , and December 31, 2014 , consisted primarily of receivables from partners in jointly owned electric utility plants and wholesale sales receivables. Sale of Accounts Receivable – KCP&L and GMO KCP&L and GMO sell all of their retail electric accounts receivable to their wholly owned subsidiaries, KCP&L Receivables Company and GMO Receivables Company, respectively, which in turn sell an undivided percentage ownership interest in the accounts receivable to Victory Receivables Corporation, an independent outside investor. Each of KCP&L Receivables Company's and GMO Receivables Company's sale of the undivided percentage ownership interest in accounts receivable to Victory Receivables Corporation is accounted for as a secured borrowing with accounts receivable pledged as collateral and a corresponding short-term collateralized note payable recognized on the balance sheets. At June 30, 2015 , and December 31, 2014 , Great Plains Energy's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $163.0 million and $171.0 million , respectively. At June 30, 2015 , and December 31, 2014 , KCP&L's accounts receivable pledged as collateral and the corresponding short-term collateralized note payable were $110.0 million . KCP&L and GMO each sell their receivables at a fixed price based upon the expected cost of funds and charge-offs. These costs comprise KCP&L's and GMO's loss on the sale of accounts receivable. KCP&L and GMO service the receivables and each receive an annual servicing fee of 1.5% of the outstanding principal amount of the receivables sold to KCP&L Receivables Company and GMO Receivables Company. KCP&L and GMO do not recognize a servicing asset or liability because management determined the collection agent fees earned by KCP&L and GMO approximate market value. KCP&L's agreement expires in September 2015 and allows for $110 million in aggregate outstanding principal amount at any time. GMO's agreement expires in September 2015 and allows for $65 million in aggregate outstanding principal from mid-November 2014 through mid-June 2015 and then increases to $80 million through September 2015. KCP&L and GMO expect to renew these agreements for at least one year. Information regarding KCP&L's sale of accounts receivable to KCP&L Receivables Company and GMO's sale of accounts receivable to GMO Receivables Company is reflected in the following tables. Three Months Ended June 30, 2015 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (388.7 ) $ 388.7 $ — $ (200.6 ) $ 200.6 $ — Gain (loss) on sale of accounts receivable (a) (4.9 ) 4.5 (0.4 ) (2.5 ) 2.3 (0.6 ) Servicing fees received (paid) 0.6 (0.6 ) — 0.3 (0.3 ) — Fees paid to outside investor — (0.2 ) (0.2 ) — (0.1 ) (0.3 ) Cash from customers (transferred) received (356.3 ) 356.3 — (183.5 ) 183.5 — Cash received from (paid for) receivables purchased 351.8 (351.8 ) — 181.3 (181.3 ) — Interest on intercompany note received (paid) — — — 0.1 (0.1 ) — Year to Date June 30, 2015 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (738.5 ) $ 738.5 $ — $ (389.3 ) $ 389.3 $ — Gain (loss) on sale of accounts receivable (a) (9.3 ) 9.0 (0.3 ) (4.9 ) 4.7 (0.5 ) Servicing fees received (paid) 1.2 (1.2 ) — 0.6 (0.6 ) — Fees paid to outside investor — (0.4 ) (0.4 ) — (0.2 ) (0.6 ) Cash from customers (transferred) received (716.1 ) 716.1 — (378.3 ) 378.3 — Cash received from (paid for) receivables purchased 707.1 (707.1 ) — 373.6 (373.6 ) — Interest on intercompany note received (paid) 0.1 (0.1 ) — 0.1 (0.1 ) — Three Months Ended June 30, 2014 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (380.9 ) $ 380.9 $ — $ (197.9 ) $ 197.9 $ — Gain (loss) on sale of accounts receivable (a) (4.8 ) 4.4 (0.4 ) (2.5 ) 2.2 (0.7 ) Servicing fees received (paid) 0.6 (0.6 ) — 0.3 (0.3 ) — Fees paid to outside investor — (0.3 ) (0.3 ) — (0.1 ) (0.4 ) Cash from customers (transferred) received (348.2 ) 348.2 — (176.5 ) 176.5 — Cash received from (paid for) receivables purchased 343.8 (343.8 ) — 174.3 (174.3 ) — Interest on intercompany note received (paid) 0.1 (0.1 ) — — — — Year to Date June 30, 2014 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (734.0 ) $ 734.0 $ — $ (391.7 ) $ 391.7 $ — Gain (loss) on sale of accounts receivable (a) (9.3 ) 9.0 (0.3 ) (5.0 ) 4.7 (0.6 ) Servicing fees received (paid) 1.2 (1.2 ) — 0.6 (0.6 ) — Fees paid to outside investor — (0.6 ) (0.6 ) — (0.3 ) (0.9 ) Cash from customers (transferred) received (715.8 ) 715.8 — (377.3 ) 377.3 — Cash received from (paid for) receivables purchased 706.8 (706.8 ) — 372.6 (372.6 ) — Interest on intercompany note received (paid) 0.1 (0.1 ) — — — —

Nuclear Plant

Nuclear Plant	6 Months Ended
	Jun. 30, 2015
Nuclear Plant [Abstract]
Nuclear Plant	4. NUCLEAR PLANT KCP&L owns 47% of Wolf Creek Generating Station (Wolf Creek), its only nuclear generating unit. Wolf Creek is located in Coffey County, Kansas, just northeast of Burlington, Kansas. Wolf Creek's operating license expires in 2045. Wolf Creek is regulated by the Nuclear Regulatory Commission (NRC), with respect to licensing, operations and safety-related requirements. Spent Nuclear Fuel and High-Level Radioactive Waste Under the Nuclear Waste Policy Act of 1982, the Department of Energy (DOE) is responsible for the permanent disposal of spent nuclear fuel. Wolf Creek paid the DOE a quarterly fee of one-tenth of a cent for each kilowatt hour (kWh) of net nuclear generation delivered and sold for the future disposal of spent nuclear fuel. KCP&L's 47% share of these costs were charged to fuel expense. The Nuclear Energy Institute, a number of individual utilities, and the National Association of Regulatory Utility Commissioners sued the DOE seeking the suspension of this fee. In January 2014, the DOE submitted a proposal to Congress to set the fee at zero, which became effective on May 16, 2014. In 2010, the DOE filed a motion with the NRC to withdraw its then pending application to the NRC to construct a national repository for the disposal of spent nuclear fuel and high-level radioactive waste at Yucca Mountain, Nevada. An NRC board denied the DOE's motion to withdraw its application. In 2011, the NRC reexamined its decision and ordered the licensing board, consistent with budgetary limitations, to close out its work on the DOE's application. In August 2013, a federal court of appeals ruled that the NRC must resume its review of the DOE's application. Wolf Creek is currently evaluating alternatives for expanding its existing on-site spent nuclear fuel storage to provide additional capacity prior to 2025. Management cannot predict when, or if, an off-site storage site or alternative disposal site will be available to receive Wolf Creek's spent nuclear fuel and will continue to monitor this activity. Low-Level Radioactive Waste Wolf Creek disposes of most of its low-level radioactive waste (Class A waste) at an existing third-party repository in Utah. Management expects that the site located in Utah will remain available to Wolf Creek for disposal of its Class A waste. Wolf Creek has contracted with a waste processor that will process, take title and dispose in another state most of the remainder of Wolf Creek's low-level radioactive waste (Classes B and C waste, which is higher in radioactivity but much lower in volume). Should on-site waste storage be needed in the future, Wolf Creek has current storage capacity on site for about four years' generation of Classes B and C waste and believes it will be able to expand that storage capacity as needed if it becomes necessary to do so. Nuclear Decommissioning Trust Fund The following table summarizes the change in Great Plains Energy's and KCP&L's nuclear decommissioning trust fund. June 30 December 31 Decommissioning Trust (millions) Beginning balance January 1 $ 199.0 $ 183.9 Contributions 1.6 3.3 Earned income, net of fees 1.5 3.6 Net realized gains 0.8 0.4 Net unrealized gains 0.4 7.8 Ending balance $ 203.3 $ 199.0 The nuclear decommissioning trust is reported at fair value on the balance sheets and is invested in assets as detailed in the following table. June 30, 2015 December 31, 2014 Cost Basis Unrealized Gains Unrealized Losses Fair Value Cost Basis Unrealized Gains Unrealized Losses Fair Value (millions) Equity securities $ 88.5 $ 52.2 $ (0.6 ) $ 140.1 $ 87.2 $ 50.6 $ (0.7 ) $ 137.1 Debt securities 57.9 2.8 (0.4 ) 60.3 55.4 3.8 (0.1 ) 59.1 Other 2.9 — — 2.9 2.8 — — 2.8 Total $ 149.3 $ 55.0 $ (1.0 ) $ 203.3 $ 145.4 $ 54.4 $ (0.8 ) $ 199.0 The weighted average maturity of debt securities held by the trust at June 30, 2015 , was approximately 7 years. The costs of securities sold are determined on the basis of specific identification. The following table summarizes the realized gains and losses from the sale of securities in the nuclear decommissioning trust fund. Three Months Ended Year to Date 2015 2014 2015 2014 (millions) Realized gains $ 1.2 $ 0.5 $ 2.6 $ 0.7 Realized losses (1.2 ) (0.5 ) (1.8 ) (0.6 )

Regulatory Matters

Regulatory Matters	6 Months Ended
	Jun. 30, 2015
Regulated Operations [Abstract]
Regulatory Matters	5 . REGULATORY MATTERS KCP&L Kansas Rate Case Proceedings In January 2015, KCP&L filed an application with The State Corporation Commission of the State of Kansas (KCC) to request an increase to its retail revenues of $67.3 million , with a return on equity of 10.3% and a rate-making equity ratio of 50.48% . The request includes costs to install environmental upgrades at the La Cygne Station, upgrades at Wolf Creek and other infrastructure and system improvements made to be able to provide reliable electric service. Testimony from KCC staff and other parties regarding the case was filed in May 2015. The KCC staff's testimony recommended a return on equity of 9.25% and a revenue increase of $44 million . In June 2015, KCP&L and KCC staff filed a unanimous partial settlement agreement that would resolve most issues in the case, except return on equity and a few other issues. The partial settlement agreement is pending KCC approval. The outcome of the KCP&L Kansas rate case will likely be different from either of the positions of KCP&L or KCC staff, though the decision of the KCC cannot be predicted. New rates will be effective on October 1, 2015. KCP&L Missouri Rate Case Proceedings In October 2014, KCP&L filed an application with the Public Service Commission of the State of Missouri (MPSC) to request an increase to its retail revenues of $120.9 million , with a return on equity of 10.3% and a rate-making equity ratio of 50.36% . The request includes recovery of increased transmission and property tax expenses, costs to install environmental upgrades at the La Cygne Station, upgrades at Wolf Creek and other infrastructure and system improvements made to be able to provide reliable electric service. KCP&L also requested authorization to implement a Fuel Adjustment Clause (FAC). True-up testimony from KCP&L, MPSC staff and other parties regarding the case was filed in July 2015. Several issues in the case have been resolved and are reflected in the true-up testimony of KCP&L and MPSC staff. KCP&L's true-up testimony requests an increase to its retail revenues of $112.7 million , with a return on equity of 10.3% . The MPSC staff's true-up testimony recommended a return on equity range from 9.0% to 9.5% and a revenue increase range of approximately $76.8 million to $87.3 million . KCP&L's request to implement a FAC is still pending MPSC approval. The outcome of the KCP&L Missouri rate case will likely be different from either of the positions of KCP&L or MPSC staff, though the decision of the MPSC cannot be predicted. New rates will be effective on or around September 30, 2015.

Asset Retirement Obligations

Asset Retirement Obligations	6 Months Ended
	Jun. 30, 2015
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations [Text Block]	6. ASSET RETIREMENT OBLIGATIONS Asset retirement obligations (AROs) associated with tangible long-lived assets are legal obligations that exist under enacted laws, statutes and written or oral contracts, including obligations arising under the doctrine of promissory estoppel. These liabilities are recognized at estimated fair value as incurred with a corresponding amount capitalized as part of the cost of the related long-lived assets and depreciated over their useful lives. Accretion of the liabilities due to the passage of time is recorded to a regulatory asset and/or liability. Changes in the estimated fair values of the liabilities are recognized when known. KCP&L has AROs related to decommissioning Wolf Creek, site remediation of its Spearville Wind Energy Facilities, asbestos abatement, removal of storage tanks and closure of ponds and landfills containing coal combustion residuals (CCRs). GMO has AROs related to asbestos abatement, removal of storage tanks and closure of ponds and landfills containing CCRs. Additionally, certain wiring used in Great Plains Energy's and KCP&L's generating stations include asbestos insulation, which would require special handling if disturbed. Due to the inability to reasonably estimate the quantities or the amount of disturbance that will be necessary during dismantlement at the end of the life of a plant, the fair value of this ARO cannot be reasonably estimated at this time. Management will continue to monitor the obligation and will recognize a liability in the period in which sufficient information becomes available to reasonably estimate its fair value. On April 17, 2015, the Environmental Protection Agency (EPA) published new regulations to regulate the disposal of CCRs at electric generating facilities. See Note 11 under the heading Solid Waste for additional information regarding the CCR rule. The CCR rule represents legal obligations of Great Plains Energy and KCP&L as to the closure of its ponds and landfills containing CCRs. As a result of the CCR rule, Great Plains Energy and KCP&L increased their AROs $69.5 million and $51.3 million , respectively. The following table summarizes the change in Great Plains Energy's and KCP&L's AROs. Great Plains Energy KCP&L June 30 December 31 June 30 December 31 2015 2014 2015 2014 (millions) Beginning balance $ 195.9 $ 158.8 $ 177.7 $ 141.7 Additions 54.5 — 34.6 — Revision in timing and/or estimates 15.0 26.8 16.7 26.8 Accretion 6.1 10.3 5.6 9.2 Ending balance $ 271.5 $ 195.9 $ 234.6 $ 177.7

Pension Plans and Other Employe

Pension Plans and Other Employee Benefits	6 Months Ended
	Jun. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Pension Plans and Other Employee Benefits	7. PENSION PLANS AND OTHER EMPLOYEE BENEFITS Great Plains Energy maintains defined benefit pension plans for substantially all active and inactive employees, including officers, of KCP&L and GMO, and its 47% ownership share of Wolf Creek Nuclear Operating Corporation (WCNOC) defined benefit plans. For the majority of employees, pension benefits under these plans reflect the employees' compensation, years of service and age at retirement; however, for union employees hired after October 1, 2013, the benefits are derived from a cash balance account formula. Effective in 2014, the KCP&L non-union plan was closed to future employees. Great Plains Energy also provides certain post-retirement health care and life insurance benefits for substantially all retired employees of KCP&L, GMO and its 47% ownership share of WCNOC. KCP&L and GMO record pension and post-retirement expense in accordance with rate orders from the MPSC and KCC that allow the difference between pension and post-retirement costs under GAAP and costs for ratemaking to be recognized as a regulatory asset or liability. This difference between financial and regulatory accounting methods is due to timing and will be eliminated over the life of the plans. The following tables provides Great Plains Energy's components of net periodic benefit costs prior to the effects of capitalization and sharing with joint owners of power plants. Pension Benefits Other Benefits Three Months Ended June 30 2015 2014 2015 2014 Components of net periodic benefit costs (millions) Service cost $ 11.3 $ 9.0 $ 0.9 $ 0.9 Interest cost 12.6 12.7 1.7 2.0 Expected return on plan assets (12.9 ) (12.7 ) (0.8 ) (0.7 ) Prior service cost 0.2 0.2 0.8 0.8 Recognized net actuarial loss 12.8 12.4 0.1 — Transition obligation — — — 0.1 Net periodic benefit costs before regulatory adjustment 24.0 21.6 2.7 3.1 Regulatory adjustment (2.6 ) (0.4 ) 1.4 1.1 Net periodic benefit costs $ 21.4 $ 21.2 $ 4.1 $ 4.2 Pension Benefits Other Benefits Year to Date June 30 2015 2014 2015 2014 Components of net periodic benefit costs (millions) Service cost $ 22.6 $ 18.1 $ 1.7 $ 1.8 Interest cost 25.2 25.4 3.4 4.0 Expected return on plan assets (25.8 ) (25.4 ) (1.5 ) (1.4 ) Prior service cost 0.4 0.4 1.6 1.6 Recognized net actuarial loss 25.6 24.8 0.1 — Transition obligation — — — 0.1 Net periodic benefit costs before regulatory adjustment 48.0 43.3 5.3 6.1 Regulatory adjustment (5.8 ) (0.8 ) 2.8 2.2 Net periodic benefit costs $ 42.2 $ 42.5 $ 8.1 $ 8.3 Year to date June 30, 2015 , Great Plains Energy contributed $36.3 million to the pension plans and expects to contribute an additional $42.6 million in 2015 to satisfy the minimum Employee Retirement Income Security Act of 1974, as amended (ERISA) funding requirements and the MPSC and KCC rate orders, the majority of which is expected to be paid by KCP&L. Also in 2015 , Great Plains Energy expects to make contributions of $10.2 million to the post-retirement benefit plans, the majority of which is expected to be paid by KCP&L.

Equity Compensation

Equity Compensation	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Compensation	8. EQUITY COMPENSATION Great Plains Energy's Long-Term Incentive Plan is an equity compensation plan approved by Great Plains Energy's shareholders. The Long-Term Incentive Plan permits the grant of restricted stock, restricted stock units, bonus shares, stock options, stock appreciation rights, limited stock appreciation rights, director shares, director deferred share units and performance shares to directors, officers and other employees of Great Plains Energy and KCP&L. Forfeiture rates are based on historical forfeitures and future expectations and are reevaluated annually. The following table summarizes Great Plains Energy's and KCP&L's equity compensation expense and the associated income tax benefit. Three Months Ended Year to Date 2015 2014 2015 2014 Great Plains Energy (millions) Equity compensation expense $ 1.1 $ 1.0 $ 0.9 $ 5.4 Income tax benefit 0.3 0.3 0.3 2.0 KCP&L Equity compensation expense $ 0.7 $ 0.7 $ 0.6 $ 3.8 Income tax benefit 0.2 0.3 0.2 1.4 Performance Shares Performance share activity year to date June 30, 2015 , is summarized in the following table. Performance adjustment represents the number of shares of common stock issued related to performance shares and can vary from the number of performance shares initially granted depending on Great Plains Energy's performance over a stated period of time. Performance Shares Grant Date Fair Value* Beginning balance January 1, 2015 534,016 $ 25.11 Granted 228,049 24.06 Earned (25,844 ) 19.48 Performance adjustment (77,515 ) 19.48 Ending balance June 30, 2015 658,706 25.63 * weighted-average At June 30, 2015 , the remaining weighted-average contractual term was 1.5 years. There were no shares granted for the three months ended June 30, 2015 , and 2014 , respectively. The weighted-average grant-date fair value of shares granted was $24.06 and $28.78 year to date June 30, 2015 , and 2014 , respectively. At June 30, 2015 , there was $8.9 million of total unrecognized compensation expense, net of forfeiture rates, related to performance shares granted under the Long-Term Incentive Plan, which will be recognized over the remaining weighted-average contractual term. The total fair value of performance shares earned and paid was $0.5 million and $2.8 million year to date June 30, 2015 , and 2014 , respectively. The fair value of performance share awards is estimated using the market value of the Company's stock at the valuation date and a Monte Carlo simulation technique that incorporates assumptions for inputs of expected volatilities, dividend yield and risk-free rates. Expected volatility is based on daily stock price change during a historical period commensurate with the remaining term of the performance period of the grant. The risk-free rate is based upon the rate at the time of the evaluation for zero-coupon government bonds with a maturity consistent with the remaining performance period of the grant. The dividend yield is based on the most recent dividends paid and the actual closing stock price on the valuation date. For shares granted in 2015 , inputs for expected volatility, dividend yield and risk-free rates were 16% , 3.72% and 1.02% , respectively. Restricted Stock Restricted stock activity year to date June 30, 2015 , is summarized in the following table. Nonvested Restricted Stock Grant Date Fair Value* Beginning balance January 1, 2015 267,390 $ 22.31 Granted and issued 77,937 26.18 Vested (103,861 ) 19.77 Ending balance June 30, 2015 241,466 24.65 * weighted-average At June 30, 2015 , the remaining weighted-average contractual term was 1.7 years. There were no shares granted for the three months ended June 30, 2015 . The weighted-average grant-date fair value of shares granted was $26.18 year to date June 30, 2015 . The weighted-average grant-date fair value of shares granted was $25.54 and $25.72 for the three months ended and year to date June 30, 2014 , respectively. At June 30, 2015 , there was $3.2 million of total unrecognized compensation expense, net of forfeiture rates, related to nonvested restricted stock granted under the Long-Term Incentive Plan, which will be recognized over the remaining weighted-average contractual term. The total fair value of shares vested was $0.1 million and $2.0 million for the three months ended and year to date June 30, 2015 . The total fair value of shares vested was $0.2 million and $1.5 million for the three months ended and year to date June 30, 2014 , respectively.

Short-term Borrowings and Short

Short-term Borrowings and Short-term Bank Lines of Credit	6 Months Ended
	Jun. 30, 2015
Short-term Borrowings and Short-term Bank Lines of Credit [Abstract]
Short-term Borrowings and Short-term Bank Lines of Credit [Text Block]	9 . SHORT-TERM BORROWINGS AND SHORT-TERM BANK LINES OF CREDIT Great Plains Energy's $200 Million Revolving Credit Facility Great Plains Energy's $200 million revolving credit facility with a group of banks expires in October 2019 . The facility's terms permit transfers of unused commitments between this facility and the KCP&L and GMO facilities discussed below, with the total amount of the facility not exceeding $400 million at any one time. In May 2015, GMO transferred $50 million of unused commitments to Great Plains Energy and Great Plains Energy transferred $200 million in unused commitments to KCP&L. A default by Great Plains Energy or any of its significant subsidiaries on other indebtedness totaling more than $50.0 million is a default under the facility. Under the terms of this facility, Great Plains Energy is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times. At June 30, 2015 , Great Plains Energy was in compliance with this covenant. At June 30, 2015 , Great Plains Energy had $11.0 million of outstanding cash borrowings at a weighted-average interest rate of 1.69% and had issued $0.2 million in letters of credit under the credit facility. At December 31, 2014 , Great Plains Energy had $4.0 million of outstanding cash borrowings at a weighted-average interest rate of 1.69% and had issued no letters of credit under the credit facility. KCP&L's $600 Million Revolving Credit Facility and Commercial Paper KCP&L's $600 million revolving credit facility with a group of banks provides support for its issuance of commercial paper and other general corporate purposes and expires in October 2019 . Great Plains Energy and KCP&L may transfer up to $200 million of unused commitments between Great Plains Energy's and KCP&L's facilities. In May 2015, Great Plains Energy transferred $200 million of unused commitments to KCP&L. A default by KCP&L on other indebtedness totaling more than $50.0 million is a default under the facility. Under the terms of this facility, KCP&L is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times. At June 30, 2015 , KCP&L was in compliance with this covenant. At June 30, 2015 , KCP&L had $484.0 million of commercial paper outstanding at a weighted-average interest rate of 0.49% , had issued letters of credit totaling $2.7 million and had no outstanding cash borrowings under the credit facility. At December 31, 2014 , KCP&L had $358.3 million of commercial paper outstanding at a weighted-average interest rate of 0.48% , had issued letters of credit totaling $2.7 million and had no outstanding cash borrowings under the credit facility. GMO's $450 Million Revolving Credit Facility and Commercial Paper GMO's $450 million revolving credit facility with a group of banks provides support for its issuance of commercial paper and other general corporate purposes and expires in October 2019 . Great Plains Energy and GMO may transfer up to $200 million of unused commitments between Great Plains Energy's and GMO's facilities. In May 2015, GMO transferred $50 million of unused commitments to Great Plains Energy. A default by GMO or any of its significant subsidiaries on other indebtedness totaling more than $50.0 million is a default under the facility. Under the terms of this facility, GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times. At June 30, 2015 , GMO was in compliance with this covenant. At June 30, 2015 , GMO had $145.3 million of commercial paper outstanding at a weighted-average interest rate of 0.45% , had issued letters of credit totaling $3.0 million and had no outstanding cash borrowings under the credit facility. At December 31, 2014 , GMO had no commercial paper outstanding, had issued letters of credit totaling $3.2 million and had no outstanding cash borrowings under the credit facility.

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Long-Term Debt	10. LONG-TERM DEBT Great Plains Energy's and KCP&L's long-term debt is detailed in the following table. June 30 December 31 Year Due 2015 2014 KCP&L (millions) General Mortgage Bonds 2.83% EIRR bonds (a) 2017-2035 $ 132.4 $ 146.4 7.15% Series 2009A (8.59% rate) (b) 2019 400.0 400.0 4.65% EIRR Series 2005 2035 50.0 50.0 Senior Notes 5.85% Series (5.72% rate) (b) 2017 250.0 250.0 6.375% Series (7.49% rate) (b) 2018 350.0 350.0 3.15% Series 2023 300.0 300.0 6.05% Series (5.78% rate) (b) 2035 250.0 250.0 5.30% Series 2041 400.0 400.0 EIRR Bonds 0.08% Series 2007A and 2007B (c) 2035 146.5 146.5 2.875% Series 2008 2038 23.4 23.4 Current maturities — (14.0 ) Unamortized discount (3.7 ) (3.8 ) Total KCP&L excluding current maturities 2,298.6 2,298.5 Other Great Plains Energy GMO First Mortgage Bonds 9.44% Series 2016-2021 6.8 7.9 GMO Senior Notes 8.27% Series 2021 80.9 80.9 3.49% Series A 2025 125.0 125.0 4.06% Series B 2033 75.0 75.0 4.74% Series C 2043 150.0 150.0 GMO Medium Term Notes 7.33% Series 2023 3.0 3.0 7.17% Series 2023 7.0 7.0 Great Plains Energy Senior Notes 6.875% Series (7.33% rate) (b) 2017 100.0 100.0 4.85% Series 2021 350.0 350.0 5.292% Series 2022 287.5 287.5 Current maturities (1.1 ) (1.1 ) Unamortized discount and premium, net 4.0 4.3 Total Great Plains Energy excluding current maturities $ 3,486.7 $ 3,488.0 (a) Weighted-average interest rates at June 30, 2015 (b) Rate after amortizing gains/losses recognized in OCI on settlements of interest rate hedging instruments (c) Variable rate KCP&L General Mortgage Bonds In March 2015, KCP&L repaid its $14.0 million secured Series 2005 Environmental Improvement Revenue Refunding (EIRR) bonds at maturity.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11 . COMMITMENTS AND CONTINGENCIES Environmental Matters Great Plains Energy and KCP&L are subject to extensive federal, state and local environmental laws, regulations and permit requirements relating to air and water quality, waste management and disposal, natural resources and health and safety. In addition to imposing continuing compliance obligations and remediation costs, these laws, regulations and permits authorize the imposition of substantial penalties for noncompliance, including fines, injunctive relief and other sanctions. The cost of complying with current and future environmental requirements is expected to be material to Great Plains Energy and KCP&L. Failure to comply with environmental requirements or to timely recover environmental costs through rates could have a material effect on Great Plains Energy's and KCP&L's results of operations, financial position and cash flows. Great Plains Energy's and KCP&L's current estimates of capital expenditures (exclusive of Allowance for Funds Used During Construction (AFUDC) and property taxes) over the next five years to comply with environmental regulations are in the following table. The total cost of compliance with any existing, proposed or future laws and regulations may be significantly different from these cost estimates provided. 2015 2016 2017 2018 2019 (millions) Great Plains Energy $ 119.1 $ 62.2 $ 158.4 $ 103.4 $ 99.9 KCP&L 104.5 51.5 132.9 86.9 84.3 The Companies expect to seek recovery of the costs associated with environmental requirements through rate increases; however, there can be no assurance that such rate increases would be granted. The Companies may be subject to materially adverse rate treatment in response to competitive, economic, political, legislative or regulatory factors and/or public perception of the Companies' environmental reputation. The following discussion groups environmental and certain associated matters into the broad categories of air and climate change, water, solid waste and remediation. Clean Air Act and Climate Change Overview The Clean Air Act and associated regulations enacted by the EPA form a comprehensive program to preserve and enhance air quality. States are required to establish regulations and programs to address all requirements of the Clean Air Act and have the flexibility to enact more stringent requirements. All of Great Plains Energy's and KCP&L's generating facilities, and certain of their other facilities, are subject to the Clean Air Act. Best Available Retrofit Technology (BART) Rule The EPA BART rule directs state air quality agencies to identify whether visibility-reducing emissions from sources subject to BART are below limits set by the state or whether retrofit measures are needed to reduce emissions. BART applies to specific eligible facilities including KCP&L's La Cygne Nos. 1 and 2 in Kansas; KCP&L's Iatan No. 1, in which GMO has an 18% interest, and KCP&L's Montrose No. 3 in Missouri; GMO's Sibley Unit No. 3 and Lake Road Unit No. 6 in Missouri; and Westar Energy, Inc.'s (Westar) Jeffrey Unit Nos. 1 and 2 in Kansas, in which GMO has an 8% interest. Both Missouri and Kansas have approved BART plans. KCP&L has a consent agreement with the Kansas Department of Health and Environment (KDHE) incorporating limits for stack particulate matter emissions, as well as limits for NO x and SO 2 emissions, at its La Cygne Station that will be below the presumptive limits under BART. KCP&L further agreed to use its best efforts to install emission control technologies to reduce those emissions from the La Cygne Station prior to the required compliance date under BART, but in no event later than June 1, 2015. In August 2011, KCC issued its order on KCP&L's predetermination request that would apply to the recovery of costs for its 50% share of the environmental equipment required to comply with BART at the La Cygne Station. In the order, KCC stated that KCP&L's decision to retrofit La Cygne was reasonable, reliable, efficient and prudent and the $1.23 billion cost estimate is reasonable. If the cost for the project is at or below the $1.23 billion estimate, absent a showing of fraud or other intentional imprudence, KCC stated that it will not re-evaluate the prudency of the cost of the project. KCP&L expects the final cost of the project to be approximately $75 million below the $1.23 billion cost estimate. KCP&L's 50% share of the estimated cost is $615 million . In September 2011, KCP&L commenced construction of the La Cygne Station project and at June 30, 2015 , had incurred approximately $524 million of cash capital expenditures. The remaining cash capital expenditures are included in the estimated capital expenditures table above. The environmental equipment was placed in-service at La Cygne No. 2 in March 2015 and at La Cygne No. 1 in April 2015. Mercury and Air Toxics Standards (MATS) Rule In December 2011, the EPA finalized the MATS Rule that will reduce emissions of toxic air pollutants, also known as hazardous air pollutants, from new and existing coal- and oil-fired electric utility generating units with a capacity of greater than 25 MWs. The rule establishes numerical emission limits for mercury, particulate matter (a surrogate for non-mercury metals) and hydrochloric acid (a surrogate for acid gases). The rule establishes work practices, instead of numerical emission limits, for organic air toxics, including dioxin/furan. MATS Rule compliance commenced at KCP&L’s Iatan Station in April 2015 and will commence at KCP&L's La Cygne Station in December 2015. In June 2015, the U.S. Supreme Court reversed the judgment of the Court of Appeals for the D.C. Circuit, which had upheld the MATS Rule, and remanded the MATS Rule for further proceedings consistent with its opinion. The Supreme Court held that the EPA was required by the Clean Air Act, but had failed, to consider costs when the EPA made the initial decision that regulating air toxics was appropriate and necessary. KCP&L’s and GMO’s other affected coal-fired units will take actions to be compliant in April 2016, unless the D.C. Circuit Court issues an order which results in alternate compliance actions. Estimated costs to comply with the MATS Rule are included in the estimated capital expenditures table above. Industrial Boiler Rule In December 2012, the EPA issued a final rule that would reduce emissions of hazardous air pollutants from new and existing industrial boilers. The final rule establishes numeric emission limits for mercury, particulate matter (as a surrogate for non-mercury metals), hydrogen chloride (as a surrogate for acid gases) and carbon monoxide (as a surrogate for non-dioxin organic hazardous air pollutants). The final rule establishes emission limits for KCP&L's and GMO's existing units that produce steam other than for the generation of electricity. The final rule does not apply to KCP&L's and GMO's electricity generating boilers, but would apply to most of GMO's Lake Road boilers, which also serve steam customers, and to auxiliary boilers at other generating facilities. The rule became effective in January 2013 and allows three to four years for compliance. Estimated costs to comply with the Industrial Boiler Rule are included in the estimated capital expenditures table above. SO 2 NAAQS In June 2010, the EPA adopted a more stringent primary National Ambient Air Quality Standard (NAAQS) for SO 2 by establishing a new 1-hour standard at a level of 0.075 ppm and revoking the two existing primary standards of 0.140 ppm evaluated over 24 hours and 0.030 ppm evaluated over an entire year. In July 2013, the EPA designated a part of Jackson County, Missouri, which is in the Companies' service territory, as a nonattainment area for the new 1-hour SO 2 standard. The Missouri Department of Natural Resources (MDNR) will now develop and submit their state implementation plan to the EPA to return the area to attainment of the standard, which may include stricter controls on certain industrial facilities. The Companies are unable to determine if there will be any financial and/or operational impacts until the state implementation plan is complete. Climate Change The Companies are subject to existing greenhouse gas reporting regulations and certain greenhouse gas permitting requirements. Management believes it is possible that additional federal or relevant state or local laws or regulations could be enacted to address global climate change. At the international level, while the United States is not a current party to the international Kyoto Protocol, it has agreed to undertake certain voluntary actions under the non-binding Copenhagen Accord and pursuant to subsequent international discussions relating to climate change, including the establishment of a goal to reduce greenhouse gas emissions. International agreements legally binding on the United States may be reached in the future. Such new laws, regulations or treaties could mandate new or increased requirements to control or reduce the emission of greenhouse gases, such as CO 2 , which are created in the combustion of fossil fuels. The Companies' current generation capacity is primarily coal-fired and is estimated to produce about one ton of CO 2 per MWh, or approximately 22 million tons and 17 million tons per year for Great Plains Energy and KCP&L, respectively. Legislation concerning the reduction of emissions of greenhouse gases, including CO 2 , is being considered at the federal and state levels. The timing and effects of any such legislation cannot be determined at this time. In the absence of new Congressional mandates, the EPA is proceeding with the regulation of greenhouse gases under the existing Clean Air Act. In August 2015, the EPA finalized CO 2 emission standards for new, modified and reconstructed affected fossil-fuel-fired electric utility generating units. The standards would not apply to Great Plains Energy's and KCP&L's existing units unless the units were modified or reconstructed in the future. In August 2015, the EPA finalized its Clean Power Plan which sets CO 2 emission performance rates for existing affected fossil fuel-fired electric generating units. Specifically, the EPA translated those performance rates into a state goal measured in mass and rate based on each state’s generation mix. The states have the ability to develop their own plans for affected units to achieve either the performance rates directly or the state goals, with guidelines for the development, submittal and implementation of those plans. Nationwide, by 2030, the EPA projects the Clean Power Plan would achieve CO 2 emission reductions from the power sector of approximately 32% from CO 2 emission levels in 2005. The EPA has finalized an interim CO 2 goal rate reduction in Kansas and Missouri (average of 2022-2029) of 34% and 26% , respectively, and 2030 targets in Kansas and Missouri of 44% and 37% , respectively. The baseline for these reductions is 2012 CO 2 emissions adjusted by the EPA. The EPA has also finalized mass based CO 2 reduction goals. Great Plains Energy and KCP&L are still reviewing the recently finalized Clean Power Plan and have not yet determined the impacts. Compliance with the Clean Power Plan or greenhouse gas legislation has the potential of having significant financial and operational impacts on Great Plains Energy and KCP&L, including the potential costs and impacts of achieving compliance with limits that may be established. However, the ultimate financial and operational consequences to Great Plains Energy and KCP&L cannot be determined until such legislation is passed and/or the Clean Power Plan is reviewed. Management will continue to monitor the progress of relevant legislation and review the Clean Power Plan. The Companies are subject to existing renewable energy standards in Missouri. Management believes that national renewable energy standards are also possible. The timing, provisions and impact of such possible future requirements, including the cost to obtain and install new equipment to achieve compliance, cannot be reasonably estimated at this time. Clean Water Act The Clean Water Act and associated regulations enacted by the EPA form a comprehensive program to restore and preserve water quality. Like the Clean Air Act, states are required to establish regulations and programs to address all requirements of the Clean Water Act, and have the flexibility to enact more stringent requirements. All of Great Plains Energy's and KCP&L's generating facilities, and certain of their other facilities, are subject to the Clean Water Act. In May 2014, the EPA finalized regulations pursuant to Section 316(b) of the Clean Water Act regarding cooling water intake structures pursuant to a court approved settlement. KCP&L generation facilities with cooling water intake structures are subject to the best technology available standards based on studies completed to comply with such standards. The rule provides flexibility to work with the states to develop the best technology available to minimize aquatic species impacted by being pinned against intake screens (impingement) or drawn into cooling water systems (entrainment). Estimated costs to comply with Section 316(b) of the Clean Water Act are included in the estimated capital expenditures table above. KCP&L holds a permit from the MDNR covering water discharge from its Hawthorn Station. The permit authorizes KCP&L to, among other things, withdraw water from the Missouri River for cooling purposes and return the heated water to the Missouri River. KCP&L has applied for a renewal of this permit and the EPA has submitted an interim objection letter regarding the allowable amount of heat that can be contained in the returned water. Until this matter is resolved, KCP&L continues to operate under its current permit. KCP&L cannot predict the outcome of this matter; however, while less significant outcomes are possible, this matter may require KCP&L to reduce its generation at Hawthorn Station, install cooling towers or other technology to cool the water, or both, any of which could have a significant impact on KCP&L's results of operations, financial position and cash flows. The outcome could also affect the terms of water permit renewals at KCP&L's Iatan Station and at GMO's Sibley and Lake Road Stations. In April 2013, the EPA proposed to revise the technology-based effluent limitations guidelines and standards regulation to make the existing controls on discharges from steam electric power plants more stringent. The proposal would set the first federal limits on the levels of toxic metals in wastewater that can be discharged from power plants. The new requirements for existing power plants would be phased in between 2017 and 2022. The EPA is under a consent decree to take final action on the proposed rule by September 2015. The proposal includes a variety of options to reduce pollutants that are discharged into waterways from coal ash, air pollution control waste and other waste from steam electric power plants. Depending on the option, the proposed rule would establish new or additional requirements for wastewaters associated with the following processes and byproducts at certain KCP&L and GMO stations: flue gas desulfurization, fly ash, bottom ash, flue gas mercury control, combustion residual leachate from landfills and surface impoundments, and non-chemical metal cleaning wastes. Estimated capital costs to comply with the proposed rule are included in the estimated capital expenditures table above. Solid Waste Solid and hazardous waste generation, storage, transportation, treatment and disposal are regulated at the federal and state levels under various laws and regulations. In December 2014, the EPA finalized regulations to regulate CCRs under the Resource Conservation and Recovery Act (RCRA) subtitle D to address the risks from the disposal of CCRs generated from the combustion of coal at electric generating facilities. The Companies use coal in generating electricity and dispose of the CCRs in both on-site facilities and facilities owned by third parties. The rule requires periodic assessments; groundwater monitoring; location restrictions; design and operating requirements; recordkeeping and notifications; and closure, among other requirements, for CCR units. The rule was promulgated in the Federal Register on April 17, 2015, and is effective six months after promulgation with various obligations effective at specified times within the rule. Estimated capital costs to comply with the CCR rule are included in the estimated capital expenditures table above. See Note 6 for information regarding an increase in Great Plains Energy's and KCP&L's AROs as a result of the CCR rule. Remediation Certain federal and state laws, including the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), hold current and previous owners or operators of contaminated facilities and persons who arranged for the disposal or treatment of hazardous substances liable for the cost of investigation and cleanup. CERCLA and other laws also authorize the EPA and other agencies to issue orders compelling potentially responsible parties to clean up sites that are determined to present an actual or potential threat to human health or the environment. GMO is named as a potentially responsible party at a disposal site for polychlorinated biphenyl (PCB) contamination, and retains some environmental liability for several operations and investments it no longer owns. In addition, GMO also owns, or has acquired liabilities from companies that once owned or operated, former manufactured gas plant (MGP) sites, which are subject to the supervision of the EPA and various state environmental agencies. At June 30, 2015 , and December 31, 2014 , KCP&L had $0.3 million accrued for environmental remediation expenses, which covers ground water monitoring at a former MGP site. The amount accrued was established on an undiscounted basis and KCP&L does not currently have an estimated time frame over which the accrued amount may be paid. In addition to the $0.3 million accrual above, at June 30, 2015 , and December 31, 2014 , Great Plains Energy had $1.4 million accrued for the future investigation and remediation of certain additional GMO identified MGP sites and retained liabilities. This estimate was based upon review of the potential costs associated with conducting investigative and remedial actions at identified sites, as well as the likelihood of whether such actions will be necessary. This estimate could change materially after further investigation, and could also be affected by the actions of environmental agencies and the financial viability of other potentially responsible parties; however, given the uncertainty of these items the possible loss or range of loss in excess of the amount accrued is not estimable. GMO has pursued recovery of remediation costs from insurance carriers and other potentially responsible parties. As a result of a settlement with an insurance carrier, approximately $1.4 million in insurance proceeds less an annual deductible is available to GMO to recover qualified MGP remediation expenses. GMO would seek recovery of additional remediation costs and expenses through rate increases; however, there can be no assurance that such rate increases would be granted.

Legal Proceedings

Legal Proceedings	6 Months Ended
	Jun. 30, 2015
Legal Proceedings [Abstract]
Contingencies Disclosure [Text Block]	12. LEGAL PROCEEDINGS GMO Western Energy Crisis In response to complaints of manipulation of the California energy market, The Federal Energy Regulatory Commission (FERC) issued an order in July 2001 requiring net sellers of power in the California markets from October 2, 2000, through June 20, 2001, at prices above a FERC-determined competitive market clearing price, to make refunds to net purchasers of power in the California market during that time period. Because MPS Merchant was a net purchaser of power during the refund period, it has received approximately $8 million in refunds through settlements with certain sellers of power. MPS Merchant estimates that it is entitled to approximately $12 million in additional refunds under the standards FERC has used in this case. FERC has stated that interest will be applied to the refunds but the amount of interest has not yet been determined. In December 2001, various parties appealed the July 2001 FERC order to the United States Court of Appeals for the Ninth Circuit (Ninth Circuit) seeking review of a number of issues, including expansion of the refund period to include periods prior to October 2, 2000 (the Summer Period). MPS Merchant was a net seller of power during the Summer Period. On August 2, 2006, the Ninth Circuit issued an order finding, among other things, that FERC did not provide a sufficient justification for refusing to exercise its remedial authority under the Federal Power Act to determine whether market participants violated FERC-approved tariffs during the Summer Period. The court remanded the matter to FERC for further consideration. If FERC determines that MPS Merchant violated then-existing tariffs or laws during the Summer Period and that such violations affected market clearing prices in California, MPS Merchant could be found to owe refunds. Due to the uncertainties remaining in the case, the potential refund or range of potential refunds owed by MPS Merchant are not reasonably estimable .

Related Party Transactions and

Related Party Transactions and Relationships	6 Months Ended
	Jun. 30, 2015
Related Party Transactions [Abstract]
Related Party Transactions and Relationships	13 . RELATED PARTY TRANSACTIONS AND RELATIONSHIPS KCP&L employees manage GMO's business and operate its facilities at cost, including GMO's 18% ownership interest in KCP&L's Iatan Nos. 1 and 2. The operating expenses and capital costs billed from KCP&L to GMO were $46.2 million and $92.2 million , respectively, for the three months ended and year to date June 30, 2015 . These costs totaled $42.6 million and $87.2 million , respectively, for the three months ended and year to date June 30, 2014 . Additionally, KCP&L and GMO engage in wholesale electricity transactions with each other. KCP&L's net wholesale sales to GMO were $0.1 million and $0.2 million for the three months ended and year to date June 30, 2015 , respectively. KCP&L's net wholesale sales to GMO were $0.6 million and $11.0 million for the three months ended and year to date June 30, 2014 , respectively. KCP&L and GMO are also authorized to participate in the Great Plains Energy money pool, an internal financing arrangement in which funds may be lent on a short-term basis to KCP&L and GMO from Great Plains Energy and between KCP&L and GMO. At December 31, 2014 , KCP&L had a money pool payable to GMO of $12.6 million . The following table summarizes KCP&L's related party net receivables. June 30 December 31 2015 2014 (millions) Net receivable from GMO $ 33.8 $ 38.2 Net receivable from Great Plains Energy 20.3 18.0

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]	14. DERIVATIVE INSTRUMENTS Great Plains Energy and KCP&L are exposed to a variety of market risks including interest rates and commodity prices. Management has established risk management policies and strategies to reduce the potentially adverse effects that the volatility of the markets may have on Great Plains Energy's and KCP&L's operating results. Great Plains Energy's and KCP&L's interest rate risk management activities have included using derivative instruments to hedge against future interest rate fluctuations on anticipated debt issuances. Commodity risk management activities, including the use of certain derivative instruments, are subject to the management, direction and control of an internal commodity risk committee. Management maintains commodity price risk management strategies that use derivative instruments to reduce the effects of fluctuations in wholesale sales, fuel and purchased power expense caused by commodity price volatility. Counterparties to commodity derivatives expose Great Plains Energy and KCP&L to credit loss in the event of nonperformance. This credit loss is limited to the cost of replacing these contracts at current market rates. Derivative instruments, excluding those instruments that qualify for the normal purchases and normal sales (NPNS) election, which are accounted for by accrual accounting, are recorded on the balance sheet at fair value as an asset or liability. Changes in the fair value of derivative instruments are recognized currently in net income unless specific hedge accounting criteria are met, except hedges for KCP&L's Kansas jurisdiction and GMO's utility operations that are recorded to a regulatory asset or liability consistent with KCC and MPSC regulatory orders. Great Plains Energy and KCP&L have posted collateral, in the ordinary course of business, for the aggregate fair value of all derivative instruments with credit risk-related contingent features that are in a liability position. At June 30, 2015 , Great Plains Energy and KCP&L have posted collateral in excess of the aggregate fair value of their derivative instruments; therefore, if the credit risk-related contingent features underlying these agreements were triggered, Great Plains Energy and KCP&L would not be required to post additional collateral to their counterparties. For derivative contracts with counterparties under master netting arrangements, Great Plains Energy and KCP&L can net all receivables and payables with each respective counterparty. Commodity Risk Management KCP&L's risk management policy uses derivative instruments to mitigate exposure to market price fluctuations for wholesale power. KCP&L has designated these financial contracts as economic hedges (non-hedging derivatives). The fair values of these instruments are recorded as derivative assets or liabilities with an offsetting entry to the consolidated statements of income. KCP&L and GMO have Transmission Congestion Rights (TCRs) that they utilize to hedge against congestion costs and protect load prices in the Southwest Power Pool, Inc. (SPP) Integrated Marketplace, which began operations in March 2014. These financial contracts have been designated as economic hedges (non-hedging derivatives). The fair values of these instruments assigned to KCP&L's Missouri jurisdiction are recorded as derivative assets or liabilities with an offsetting entry recorded to electric revenue. The fair values of these instruments assigned to KCP&L's Kansas jurisdiction and GMO are recorded as derivative assets or liabilities with an offsetting entry recorded to a regulatory asset or liability. For KCP&L's Kansas jurisdiction and GMO, the settlement costs are included in their fuel recovery mechanisms. A regulatory asset or liability is recorded to reflect the change in the timing of recognition authorized by KCC and MPSC. Recovery of actual costs will not impact earnings, but will impact cash flows due to the timing of the recovery mechanism. GMO's risk management policy uses derivative instruments to mitigate price exposure to natural gas price volatility in the market. At June 30, 2015 , GMO had financial contracts in place to hedge approximately 43% , 29% and 10% of the expected on-peak natural gas generation and natural gas equivalent purchased power price exposure for the remainder of 2015 , 2016 and 2017 , respectively. The fair value of the portfolio will settle against actual purchases of natural gas and purchased power. GMO has designated its natural gas hedges as economic hedges (non-hedging derivatives). In connection with GMO's 2005 Missouri electric rate case, it was agreed that the settlement costs of these contracts would be recognized in fuel expense. The settlement cost is included in GMO's fuel recovery mechanism. A regulatory asset or liability is recorded to reflect the change in the timing of recognition authorized by the MPSC. Recovery of actual costs will not impact earnings, but will impact cash flows due to the timing of the recovery mechanism. MPS Merchant, which has certain long-term natural gas contracts remaining from its former non-regulated trading operations, manages the daily delivery of its remaining contractual commitments with economic hedges (non-hedging derivatives) to reduce its exposure to changes in market prices. Within the trading portfolio, MPS Merchant takes certain positions to hedge physical sale or purchase contracts. MPS Merchant records the fair value of physical trading energy contracts as derivative assets or liabilities with an offsetting entry to the consolidated statements of income. The gross notional contract amount and recorded fair values of open positions for derivative instruments are summarized in the following table. The fair values of these derivatives are recorded on the consolidated balance sheets. The fair values below are gross values before netting agreements and netting of cash collateral. June 30 December 31 2015 2014 Notional Contract Amount Fair Value Notional Contract Amount Fair Value Great Plains Energy (millions) Futures contracts Non-hedging derivatives $ 34.1 $ (2.9 ) $ 14.9 $ (2.4 ) Forward contracts Non-hedging derivatives 23.4 3.8 29.7 4.1 Transmission congestion rights Non-hedging derivatives 12.8 0.1 28.3 2.6 Option contracts Non-hedging derivatives — — 1.7 0.1 KCP&L Futures contracts Non-hedging derivatives $ 5.4 $ — $ — $ — Transmission congestion rights Non-hedging derivatives 9.5 0.1 23.6 3.1 The fair values of Great Plains Energy's and KCP&L's open derivative positions and balance sheet classification are summarized in the following tables. The fair values below are gross values before netting agreements and netting of cash collateral. Great Plains Energy Balance Sheet Asset Derivatives Liability Derivatives June 30, 2015 Classification Fair Value Fair Value Derivatives Not Designated as Hedging Instruments (millions) Commodity contracts Other $ 4.4 $ 3.4 December 31, 2014 Derivatives Not Designated as Hedging Instruments Commodity contracts Other $ 8.6 $ 4.2 KCP&L Balance Sheet Asset Derivatives Liability Derivatives June 30, 2015 Classification Fair Value Fair Value Derivatives Not Designated as Hedging Instruments (millions) Commodity contracts Other $ 0.5 $ 0.4 December 31, 2014 Derivatives Not Designated as Hedging Instruments Commodity contracts Other $ 4.0 $ 0.9 The following tables provide information regarding Great Plains Energy's and KCP&L's offsetting of derivative assets and liabilities. Great Plains Energy Gross Amounts Not Offset in the Statement of Financial Position Description Gross Amounts Recognized Gross Amounts Offset in the Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Financial Instruments Cash Collateral Net Amount June 30, 2015 (millions) Derivative assets $ 4.4 $ (0.5 ) $ 3.9 $ — $ — $ 3.9 Derivative liabilities 3.4 (3.3 ) 0.1 — — 0.1 December 31, 2014 Derivative assets $ 8.6 $ (1.2 ) $ 7.4 $ — $ — $ 7.4 Derivative liabilities 4.2 (3.5 ) 0.7 — — 0.7 KCP&L Gross Amounts Not Offset in the Statement of Financial Position Description Gross Amounts Recognized Gross Amounts Offset in the Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Financial Instruments Cash Collateral Net Amount June 30, 2015 (millions) Derivative assets $ 0.5 $ (0.4 ) $ 0.1 $ — $ — $ 0.1 Derivative liabilities 0.4 (0.4 ) — — — — December 31, 2014 Derivative assets $ 4.0 $ (0.9 ) $ 3.1 $ — $ — $ 3.1 Derivative liabilities 0.9 (0.9 ) — — — — At June 30, 2015 , and December 31, 2014 , Great Plains Energy offset $2.8 million and $2.3 million , respectively, of cash collateral posted with counterparties against net derivative positions. See Note 16 for information regarding amounts reclassified out of accumulated other comprehensive loss for Great Plains Energy and KCP&L. Great Plains Energy's accumulated OCI at June 30, 2015 , includes $9.2 million that is expected to be reclassified to expenses over the next twelve months. KCP&L's accumulated OCI at June 30, 2015 , includes $8.8 million that is expected to be reclassified to expenses over the next twelve months. The following tables summarize the amounts of gain (loss) recognized for the change in fair value of commodity contract derivatives not designated as hedging instruments for Great Plains Energy and KCP&L. Great Plains Energy Three Months Ended Year to Date Derivatives Not Designated as Hedging Instruments 2015 2014 2015 2014 Location of Gain (Loss) (millions) Electric revenues $ (2.5 ) $ (3.2 ) $ (7.7 ) $ (2.3 ) Fuel (0.6 ) 0.6 (1.1 ) 1.0 Purchased power (1.1 ) — (1.2 ) 0.4 Regulatory asset 3.1 (4.0 ) (3.2 ) (4.1 ) Regulatory liability — (0.9 ) — 0.2 Total $ (1.1 ) $ (7.5 ) $ (13.2 ) $ (4.8 ) KCP&L Three Months Ended Year to Date Derivatives Not Designated as Hedging Instruments 2015 2014 2015 2014 Location of Gain (Loss) (millions) Electric revenues $ (2.5 ) $ (3.2 ) $ (7.7 ) $ (2.3 ) Fuel — 0.1 0.2 0.1 Regulatory asset 1.4 (2.1 ) — (2.2 ) Total $ (1.1 ) $ (5.2 ) $ (7.5 ) $ (4.4 )

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	15. FAIR VALUE MEASUREMENTS GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. GAAP establishes a fair value hierarchy, which prioritizes the inputs to valuation techniques used to measure fair value into three broad categories, giving the highest priority to quoted prices in active markets for identical assets or liabilities and lowest priority to unobservable inputs. A definition of the various levels, as well as discussion of the various measurements within the levels, is as follows: Level 1 – Unadjusted quoted prices for identical assets or liabilities in active markets that Great Plains Energy and KCP&L have access to at the measurement date. Level 2 – Market-based inputs for assets or liabilities that are observable (either directly or indirectly) or inputs that are not observable but are corroborated by market data. Level 3 – Unobservable inputs, reflecting Great Plains Energy's and KCP&L's own assumptions about the assumptions market participants would use in pricing the asset or liability. Great Plains Energy and KCP&L record cash and cash equivalents and short-term borrowings on the balance sheet at cost, which approximates fair value due to the short-term nature of these instruments. Great Plains Energy and KCP&L record long-term debt on the balance sheet at amortized cost. The fair value of long-term debt is measured as a Level 2 liability and is based on quoted market prices, with the incremental borrowing rate for similar debt used to determine fair value if quoted market prices are not available. At June 30, 2015 , the book value and fair value of Great Plains Energy's long-term debt, including current maturities, were $3.5 billion and $3.8 billion , respectively. At December 31, 2014 , the book value and fair value of Great Plains Energy's long-term debt, including current maturities, were $3.5 billion and $3.8 billion , respectively. At June 30, 2015 , the book value and fair value of KCP&L's long-term debt, including current maturities, were $2.3 billion and $2.5 billion , respectively. At December 31, 2014 , the book value and fair value of KCP&L's long-term debt, including current maturities, were $2.3 billion and $2.6 billion , respectively. The following tables include Great Plains Energy's and KCP&L's balances of financial assets and liabilities measured at fair value on a recurring basis. The fair values below are gross values before netting arrangements and netting of cash collateral. Description June 30 Level 1 Level 2 Level 3 KCP&L (millions) Assets Nuclear decommissioning trust (a) Equity securities $ 140.1 $ 140.1 $ — $ — Debt securities U.S. Treasury 24.9 24.9 — — U.S. Agency 2.1 — 2.1 — State and local obligations 4.0 — 4.0 — Corporate bonds 28.8 — 28.8 — Foreign governments 0.5 — 0.5 — Cash equivalents 2.9 2.9 — — Total nuclear decommissioning trust 203.3 167.9 35.4 — Self-insured health plan trust (b) Equity securities 1.2 1.2 — — Debt securities 7.2 — 7.2 — Cash and cash equivalents 7.4 7.4 — — Total self-insured health plan trust 15.8 8.6 7.2 — Derivative instruments (c) 0.5 0.1 — 0.4 Total $ 219.6 $ 176.6 $ 42.6 $ 0.4 Liabilities Derivative instruments (c) 0.4 0.1 — 0.3 Total $ 0.4 $ 0.1 $ — $ 0.3 Other Great Plains Energy Assets Derivative instruments (c) $ 3.9 $ — $ 3.1 $ 0.8 SERP rabbi trusts (d) Equity securities 0.1 0.1 — — Fixed income funds 17.3 — 17.3 — Total SERP rabbi trusts 17.4 0.1 17.3 — Total 21.3 0.1 20.4 0.8 Liabilities Derivative instruments (c) 3.0 2.9 — 0.1 Total $ 3.0 $ 2.9 $ — $ 0.1 Great Plains Energy Assets Nuclear decommissioning trust (a) $ 203.3 $ 167.9 $ 35.4 $ — Self-insured health plan trust (b) 15.8 8.6 7.2 — Derivative instruments (c) 4.4 0.1 3.1 1.2 SERP rabbi trusts (d) 17.4 0.1 17.3 — Total 240.9 176.7 63.0 1.2 Liabilities Derivative instruments (c) 3.4 3.0 — 0.4 Total $ 3.4 $ 3.0 $ — $ 0.4 Description December 31 Level 1 Level 2 Level 3 KCP&L (millions) Assets Nuclear decommissioning trust (a) Equity securities $ 137.1 $ 137.1 $ — $ — Debt securities U.S. Treasury 22.9 22.9 — — U.S. Agency 3.5 — 3.5 — State and local obligations 4.1 — 4.1 — Corporate bonds 28.1 — 28.1 — Foreign governments 0.5 — 0.5 — Cash equivalents 2.3 2.3 — — Other 0.5 — 0.5 — Total nuclear decommissioning trust 199.0 162.3 36.7 — Self-insured health plan trust (b) Equity securities 1.3 1.3 — — Debt securities 7.6 — 7.6 — Cash and cash equivalents 6.2 6.2 — — Total self-insured health plan trust 15.1 7.5 7.6 — Derivative instruments (c) 4.0 — — 4.0 Total $ 218.1 $ 169.8 $ 44.3 $ 4.0 Liabilities Derivative instruments (c) 0.9 — — 0.9 Total $ 0.9 $ — $ — $ 0.9 Other Great Plains Energy Assets Derivative instruments (c) $ 4.6 $ — $ 3.4 $ 1.2 SERP rabbi trusts (d) Equity securities 0.1 0.1 — — Fixed income funds 17.8 — 17.8 — Total SERP rabbi trusts 17.9 0.1 17.8 — Total 22.5 0.1 21.2 1.2 Liabilities Derivative instruments (c) 3.3 2.4 0.1 0.8 Total $ 3.3 $ 2.4 $ 0.1 $ 0.8 Great Plains Energy Assets Nuclear decommissioning trust (a) $ 199.0 $ 162.3 $ 36.7 $ — Self-insured health plan trust (b) 15.1 7.5 7.6 — Derivative instruments (c) 8.6 — 3.4 5.2 SERP rabbi trusts (d) 17.9 0.1 17.8 — Total 240.6 169.9 65.5 5.2 Liabilities Derivative instruments (c) 4.2 2.4 0.1 1.7 Total $ 4.2 $ 2.4 $ 0.1 $ 1.7 (a) Fair value is based on quoted market prices of the investments held by the fund and/or valuation models. (b) Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities. (c) The fair value of derivative instruments is estimated using market quotes, over-the-counter forward price and volatility curves and correlations among fuel prices, net of estimated credit risk. Derivative instruments classified as Level 1 represent exchange traded derivative instruments. Derivative instruments classified as Level 2 represent non-exchange traded derivative instruments traded in over-the-counter markets. Derivative instruments classified as Level 3 represent non-exchange traded derivatives traded in over-the-counter markets for which observable market data is not available to corroborate the valuation inputs and TCRs valued at the most recent auction price in the SPP Integrated Marketplace. (d) Fair value is based on quoted market prices for equity securities and Net Asset Value (NAV) per share for fixed income funds. The fixed income fund invests primarily in intermediate and long-term debt securities, can be redeemed immediately and is not subject to any restrictions on redemptions. The following tables reconcile the beginning and ending balances for all Level 3 assets and liabilities measured at fair value on a recurring basis. Great Plains Energy Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset/(liability) at April 1 $ (1.2 ) $ 6.9 Total realized/unrealized gains (losses): included in electric revenue (2.5 ) (3.2 ) included in purchased power expense (1.1 ) — included in non-operating income 1.6 4.0 included in regulatory asset 2.0 (4.1 ) Purchases 0.4 7.3 Settlements 1.6 (10.3 ) Net asset at June 30 $ 0.8 $ 0.6 Total unrealized gains (losses) relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.4 ) included in non-operating income — 0.1 included in regulatory asset — (4.1 ) Great Plains Energy Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset at January 1 $ 3.5 $ 3.3 Total realized/unrealized gains (losses): included in electric revenue (7.7 ) (2.3 ) included in purchased power expense (1.2 ) 0.4 included in non-operating income 3.7 11.1 included in regulatory asset — (4.1 ) Purchases 0.6 13.4 Settlements 1.9 (21.2 ) Net asset at June 30 $ 0.8 $ 0.6 Total unrealized gains (losses) relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.5 ) included in non-operating income (0.1 ) 0.2 included in regulatory asset — (4.1 ) KCP&L Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset/(liability) at April 1 $ (0.8 ) $ 3.9 Total realized/unrealized gains (losses): included in electric revenue (2.5 ) (3.2 ) included in regulatory asset 1.4 (2.1 ) Purchases 0.2 6.7 Settlements 1.8 (4.4 ) Net asset at June 30 $ 0.1 $ 0.9 Total unrealized losses relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.4 ) included in regulatory asset — (2.1 ) KCP&L Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset at January 1 $ 3.1 $ 1.1 Total realized/unrealized gains (losses): included in electric revenue (7.7 ) (2.3 ) included in regulatory asset — (2.2 ) Purchases (0.2 ) 11.8 Settlements 4.9 (7.5 ) Net asset at June 30 $ 0.1 $ 0.9 Total unrealized losses relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.5 ) included in regulatory asset — (2.2 )

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	6 Months Ended
	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss) [Text Block]	16 . ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following tables reflect the change in the balances of each component of accumulated other comprehensive loss for Great Plains Energy and KCP&L. Great Plains Energy Gains and Losses on Cash Flow Hedges (a) Defined Benefit Pension Items (a) Total (a) (millions) Year to Date June 30, 2015 Beginning balance January 1 $ (15.8 ) $ (2.9 ) $ (18.7 ) Amounts reclassified from accumulated other comprehensive loss 2.8 0.3 3.1 Net current period other comprehensive income 2.8 0.3 3.1 Ending balance June 30 $ (13.0 ) $ (2.6 ) $ (15.6 ) Year to Date June 30, 2014 Beginning balance January 1 $ (23.8 ) $ (1.5 ) $ (25.3 ) Amounts reclassified from accumulated other comprehensive loss 5.3 0.2 5.5 Net current period other comprehensive income 5.3 0.2 5.5 Ending balance June 30 $ (18.5 ) $ (1.3 ) $ (19.8 ) (a) Net of tax KCP&L Gains and Losses on Cash Flow Hedges (a) (millions) Year to Date June 30, 2015 Beginning balance January 1 $ (14.9 ) Amounts reclassified from accumulated other comprehensive loss 2.7 Net current period other comprehensive income 2.7 Ending balance June 30 $ (12.2 ) Year to Date June 30, 2014 Beginning balance January 1 $ (20.2 ) Amounts reclassified from accumulated other comprehensive loss 2.7 Net current period other comprehensive income 2.7 Ending balance June 30 $ (17.5 ) (a) Net of tax The following tables reflect the effect on certain line items of net income from amounts reclassified out of each component of accumulated other comprehensive loss for Great Plains Energy and KCP&L. Great Plains Energy Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Three Months Ended June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (2.3 ) $ (3.9 ) Interest charges (2.3 ) (3.9 ) Income before income tax expense and income from equity investments 0.9 1.4 Income tax benefit $ (1.4 ) $ (2.5 ) Net income Amortization of defined benefit pension items Net losses included in net periodic benefit costs $ (0.2 ) $ (0.1 ) Utility operating and maintenance expenses (0.2 ) (0.1 ) Income before income tax expense and income from equity investments — 0.1 Income tax benefit $ (0.2 ) $ — Net income Total reclassifications, net of tax $ (1.6 ) $ (2.5 ) Net income Great Plains Energy Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Year to Date June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (4.6 ) $ (8.6 ) Interest charges (4.6 ) (8.6 ) Income before income tax expense and income from equity investments 1.8 3.3 Income tax benefit $ (2.8 ) $ (5.3 ) Net income Amortization of defined benefit pension items Net losses included in net periodic benefit costs $ (0.4 ) $ (0.3 ) Utility operating and maintenance expenses (0.4 ) (0.3 ) Income before income tax expense and income from equity investments 0.1 0.1 Income tax benefit $ (0.3 ) $ (0.2 ) Net income Total reclassifications, net of tax $ (3.1 ) $ (5.5 ) Net income KCP&L Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Three Months Ended June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (2.1 ) $ (2.2 ) Interest charges (2.1 ) (2.2 ) Income before income tax expense 0.8 0.8 Income tax benefit Total reclassifications, net of tax $ (1.3 ) $ (1.4 ) Net income KCP&L Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Year to Date June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (4.4 ) $ (4.4 ) Interest charges (4.4 ) (4.4 ) Income before income tax expense 1.7 1.7 Income tax benefit Total reclassifications, net of tax $ (2.7 ) $ (2.7 ) Net income

Taxes

Taxes	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	17. TAXES Components of income tax expense are detailed in the following tables. Three Months Ended Year to Date Great Plains Energy 2015 2014 2015 2014 Current income taxes (millions) Federal $ — $ (0.2 ) $ 0.5 $ 0.1 State — — (0.1 ) 0.1 Total — (0.2 ) 0.4 0.2 Deferred income taxes Federal 20.3 25.0 25.4 31.6 State 4.5 5.1 5.9 6.8 Total 24.8 30.1 31.3 38.4 Noncurrent income taxes Federal — (2.4 ) — (2.4 ) State — (0.3 ) — (0.3 ) Foreign — 0.2 — — Total — (2.5 ) — (2.7 ) Investment tax credit amortization (0.3 ) (0.4 ) (0.7 ) (0.8 ) Income tax expense $ 24.5 $ 27.0 $ 31.0 $ 35.1 Three Months Ended Year to Date KCP&L 2015 2014 2015 2014 Current income taxes (millions) Federal $ 4.2 $ (2.0 ) $ (1.5 ) $ 0.7 State 0.7 (0.3 ) (0.4 ) 0.2 Total 4.9 (2.3 ) (1.9 ) 0.9 Deferred income taxes Federal 7.9 14.9 16.2 15.3 State 2.4 3.3 4.4 3.9 Total 10.3 18.2 20.6 19.2 Investment tax credit amortization (0.3 ) (0.3 ) (0.5 ) (0.5 ) Income tax expense $ 14.9 $ 15.6 $ 18.2 $ 19.6 Effective Income Tax Rates Effective income tax rates reflected in the financial statements and the reasons for their differences from the statutory federal rates are detailed in the following tables. Three Months Ended Year to Date Great Plains Energy 2015 2014 2015 2014 Federal statutory income tax rate 35.0 % 35.0 % 35.0 % 35.0 % Differences between book and tax depreciation not normalized 1.3 (0.6 ) 0.8 (0.9 ) Amortization of investment tax credits (0.5 ) (0.5 ) (0.8 ) (0.7 ) Federal income tax credits (4.0 ) (3.8 ) (5.6 ) (5.4 ) State income taxes 3.8 3.8 3.7 3.8 Changes in uncertain tax positions, net — 0.3 — — Other (0.1 ) (0.2 ) (0.3 ) (0.3 ) Effective income tax rate 35.5 % 34.0 % 32.8 % 31.5 % Three Months Ended Year to Date KCP&L 2015 2014 2015 2014 Federal statutory income tax rate 35.0 % 35.0 % 35.0 % 35.0 % Differences between book and tax depreciation not normalized 2.0 (0.9 ) 1.3 (1.8 ) Amortization of investment tax credits (0.6 ) (0.5 ) (0.9 ) (0.7 ) Federal income tax credits (6.2 ) (5.9 ) (8.7 ) (8.3 ) State income taxes 4.1 3.8 4.0 3.7 Other (0.6 ) (0.5 ) (0.7 ) (0.6 ) Effective income tax rate 33.7 % 31.0 % 30.0 % 27.3 %

Segments and Related Informatio

Segments and Related Information	6 Months Ended
	Jun. 30, 2015
Segment Reporting [Abstract]
Segments and Related Information	18 . SEGMENTS AND RELATED INFORMATION Great Plains Energy has one reportable segment based on its method of internal reporting, which segregates reportable segments based on products and services, management responsibility and regulation. The one reportable business segment is electric utility, consisting of KCP&L, GMO's regulated utility operations and GMO Receivables Company. Other includes GMO activity other than its regulated utility operations, GPETHC and unallocated corporate charges. The summary of significant accounting policies applies to the reportable segment. Segment performance is evaluated based on net income. The following tables reflect summarized financial information concerning Great Plains Energy's reportable segment. Three Months Ended June 30, 2015 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 609.0 $ — $ — $ 609.0 Depreciation and amortization (83.5 ) — — (83.5 ) Interest (charges) income (47.9 ) (10.1 ) 8.0 (50.0 ) Income tax (expense) benefit (25.6 ) 1.1 — (24.5 ) Net income (loss) 46.4 (2.0 ) — 44.4 Year to Date June 30, 2015 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 1,158.1 $ — $ — $ 1,158.1 Depreciation and amortization (163.3 ) — — (163.3 ) Interest (charges) income (93.2 ) (20.1 ) 16.0 (97.3 ) Income tax (expense) benefit (33.5 ) 2.5 — (31.0 ) Net income (loss) 67.3 (4.0 ) — 63.3 Three Months Ended June 30, 2014 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 648.4 $ — $ — $ 648.4 Depreciation and amortization (75.6 ) — — (75.6 ) Interest (charges) income (46.0 ) (11.7 ) 9.4 (48.3 ) Income tax (expense) benefit (28.0 ) 1.0 — (27.0 ) Net income (loss) 54.7 (2.6 ) — 52.1 Year to Date June 30, 2014 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 1,233.5 $ — $ — $ 1,233.5 Depreciation and amortization (150.1 ) — — (150.1 ) Interest (charges) income (93.0 ) (24.3 ) 19.6 (97.7 ) Income tax (expense) benefit (37.8 ) 2.7 — (35.1 ) Net income (loss) 80.8 (4.9 ) — 75.9 Electric Utility Other Eliminations Great Plains Energy June 30, 2015 (millions) Assets $ 11,039.4 $ 126.1 $ (403.3 ) $ 10,762.2 Capital expenditures (a) 366.8 — — 366.8 December 31, 2014 Assets $ 10,746.1 $ 33.1 $ (303.5 ) $ 10,475.7 Capital expenditures (a) 773.7 — — 773.7 (a) Capital expenditures reflect year to date amounts for the periods presented.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Organization [Policy Text Block]	Organization Great Plains Energy, a Missouri corporation incorporated in 2001, is a public utility holding company and does not own or operate any significant assets other than the stock of its subsidiaries. Great Plains Energy's wholly owned direct subsidiaries with significant operations are as follows: • KCP&L is an integrated, regulated electric utility that provides electricity to customers primarily in the states of Missouri and Kansas. KCP&L has one active wholly owned subsidiary, Kansas City Power & Light Receivables Company (KCP&L Receivables Company). • KCP&L Greater Missouri Operations Company (GMO) is an integrated, regulated electric utility that provides electricity to customers in the state of Missouri. GMO also provides regulated steam service to certain customers in the St. Joseph, Missouri area. GMO has two active wholly owned subsidiaries, GMO Receivables Company and MPS Merchant Services, Inc. (MPS Merchant). MPS Merchant has certain long-term natural gas contracts remaining from its former non-regulated trading operations. Great Plains Energy also wholly owns GPE Transmission Holding Company, LLC (GPETHC). GPETHC owns 13.5% of Transource Energy, LLC (Transource) with the remaining 86.5% owned by AEP Transmission Holding Company, LLC (AEPTHC), a subsidiary of American Electric Power Company, Inc. GPETHC accounts for its investment in Transource under the equity method. Transource is focused on the development of competitive electric transmission projects. Each of Great Plains Energy's and KCP&L's consolidated financial statements includes the accounts of their subsidiaries. Intercompany transactions have been eliminated. Great Plains Energy's sole reportable business segment is electric utility. See Note 18 for additional information.
Basic and Diluted Earnings per Common Share Calculation [Policy Text Block]	Basic and Diluted Earnings per Common Share Calculation To determine basic earnings per common share (EPS), preferred stock dividend requirements are deducted from net income before dividing by the average number of common shares outstanding. The effect of dilutive securities, calculated using the treasury stock method, assumes the issuance of common shares applicable to performance shares and restricted stock.
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) No. 2014-09, Revenue from Contracts with Customers , which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in Generally Accepted Accounting Principles (GAAP) when it becomes effective. In July 2015, the FASB approved a one year deferral of the effective date of ASU No. 2014-09. A final ASU formally amending the effective date of ASU No. 2014-09 from January 1, 2017, to January 1, 2018, is expected to be issued in the third quarter of 2015. The standard permits the use of either the retrospective or cumulative effect transition method. The Companies are evaluating the effect that ASU No. 2014-09 will have on their consolidated financial statements and related disclosures. The Companies have not yet selected a transition method nor have they determined the effect of the standard on their ongoing financial reporting. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs , which requires that debt issuance costs related to a recognized debt liability be presented on the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. Great Plains Energy and KCP&L currently include debt issuance costs in Other - Investments and Other Assets on their consolidated balance sheets. The new guidance is to be applied retrospectively and is effective for interim and annual periods beginning after December 15, 2015, with early adoption permitted. The Companies intend to early adopt ASU No. 2015-03 for the 2015 Form 10-K.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following table reconciles Great Plains Energy's basic and diluted EPS. Three Months Ended Year to Date 2015 2014 2015 2014 Income (millions, except per share amounts) Net income $ 44.4 $ 52.1 $ 63.3 $ 75.9 Less: preferred stock dividend requirements 0.4 0.4 0.8 0.8 Earnings available for common shareholders $ 44.0 $ 51.7 $ 62.5 $ 75.1 Common Shares Outstanding Average number of common shares outstanding 154.1 153.8 154.1 153.8 Add: effect of dilutive securities 0.4 0.2 0.4 0.2 Diluted average number of common shares outstanding 154.5 154.0 154.5 154.0 Basic and diluted EPS $ 0.28 $ 0.34 $ 0.40 $ 0.49
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]	Anti-dilutive shares excluded from the computation of diluted EPS are detailed in the following table. Three Months Ended Year to Date 2015 2014 2015 2014 Performance shares — 475,549 — 475,549 Restricted stock shares — — — 287

Supplemental Cash Flow Inform28

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2015
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	Great Plains Energy Other Operating Activities Year to Date June 30 2015 2014 Cash flows affected by changes in: (millions) Receivables $ (36.0 ) $ (57.1 ) Accounts receivable pledged as collateral 8.0 4.0 Fuel inventories (12.2 ) 3.9 Materials and supplies 0.3 4.1 Accounts payable (108.2 ) (76.1 ) Accrued taxes 47.5 46.0 Accrued interest (1.3 ) (1.3 ) Deferred refueling outage costs (17.7 ) 8.4 Pension and post-retirement benefit obligations 25.0 5.3 Allowance for equity funds used during construction (3.5 ) (9.0 ) Fuel recovery mechanism 25.6 (17.3 ) Solar rebates paid (4.8 ) (33.3 ) Other 3.9 (5.5 ) Total other operating activities $ (73.4 ) $ (127.9 ) Cash paid during the period: Interest $ 91.9 $ 88.2 Income taxes $ 0.2 $ 0.1 Non-cash investing activities: Liabilities accrued for capital expenditures $ 34.8 $ 46.7 KCP&L Other Operating Activities Year to Date June 30 2015 2014 Cash flows affected by changes in: (millions) Receivables $ (1.4 ) $ (34.4 ) Fuel inventories (11.9 ) 6.6 Materials and supplies 0.1 2.8 Accounts payable (69.7 ) (38.8 ) Accrued taxes 94.4 31.9 Accrued interest (1.5 ) (1.5 ) Deferred refueling outage costs (17.7 ) 8.4 Pension and post-retirement benefit obligations 25.1 4.4 Allowance for equity funds used during construction (2.7 ) (8.5 ) Fuel recovery mechanism 0.6 2.4 Solar rebates paid (4.1 ) (10.7 ) Other 3.7 (15.8 ) Total other operating activities $ 14.9 $ (53.2 ) Cash paid during the period: Interest $ 61.2 $ 57.2 Non-cash investing activities: Liabilities accrued for capital expenditures $ 31.4 $ 39.3

Receivables (Tables)

Receivables (Tables)	6 Months Ended
	Jun. 30, 2015
Receivables [Abstract]
Schedule of receivables [Table Text Block]	Great Plains Energy's and KCP&L's receivables are detailed in the following table. June 30 December 31 2015 2014 Great Plains Energy (millions) Customer accounts receivable - billed $ 3.2 $ 1.1 Customer accounts receivable - unbilled 123.2 75.3 Allowance for doubtful accounts - customer accounts receivable (5.3 ) (2.8 ) Other receivables 75.1 86.7 Total $ 196.2 $ 160.3 KCP&L Customer accounts receivable - billed $ 1.1 $ 0.6 Customer accounts receivable - unbilled 77.3 49.7 Allowance for doubtful accounts - customer accounts receivable (2.8 ) (1.2 ) Other receivables 69.3 79.8 Total $ 144.9 $ 128.9
Schedule of accounts receivable sold [Table Text Block]	Information regarding KCP&L's sale of accounts receivable to KCP&L Receivables Company and GMO's sale of accounts receivable to GMO Receivables Company is reflected in the following tables. Three Months Ended June 30, 2015 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (388.7 ) $ 388.7 $ — $ (200.6 ) $ 200.6 $ — Gain (loss) on sale of accounts receivable (a) (4.9 ) 4.5 (0.4 ) (2.5 ) 2.3 (0.6 ) Servicing fees received (paid) 0.6 (0.6 ) — 0.3 (0.3 ) — Fees paid to outside investor — (0.2 ) (0.2 ) — (0.1 ) (0.3 ) Cash from customers (transferred) received (356.3 ) 356.3 — (183.5 ) 183.5 — Cash received from (paid for) receivables purchased 351.8 (351.8 ) — 181.3 (181.3 ) — Interest on intercompany note received (paid) — — — 0.1 (0.1 ) — Year to Date June 30, 2015 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (738.5 ) $ 738.5 $ — $ (389.3 ) $ 389.3 $ — Gain (loss) on sale of accounts receivable (a) (9.3 ) 9.0 (0.3 ) (4.9 ) 4.7 (0.5 ) Servicing fees received (paid) 1.2 (1.2 ) — 0.6 (0.6 ) — Fees paid to outside investor — (0.4 ) (0.4 ) — (0.2 ) (0.6 ) Cash from customers (transferred) received (716.1 ) 716.1 — (378.3 ) 378.3 — Cash received from (paid for) receivables purchased 707.1 (707.1 ) — 373.6 (373.6 ) — Interest on intercompany note received (paid) 0.1 (0.1 ) — 0.1 (0.1 ) — Three Months Ended June 30, 2014 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (380.9 ) $ 380.9 $ — $ (197.9 ) $ 197.9 $ — Gain (loss) on sale of accounts receivable (a) (4.8 ) 4.4 (0.4 ) (2.5 ) 2.2 (0.7 ) Servicing fees received (paid) 0.6 (0.6 ) — 0.3 (0.3 ) — Fees paid to outside investor — (0.3 ) (0.3 ) — (0.1 ) (0.4 ) Cash from customers (transferred) received (348.2 ) 348.2 — (176.5 ) 176.5 — Cash received from (paid for) receivables purchased 343.8 (343.8 ) — 174.3 (174.3 ) — Interest on intercompany note received (paid) 0.1 (0.1 ) — — — — Year to Date June 30, 2014 KCP&L KCP&L Receivables Company Consolidated KCP&L GMO GMO Receivables Company Consolidated Great Plains Energy (millions) Receivables (sold) purchased $ (734.0 ) $ 734.0 $ — $ (391.7 ) $ 391.7 $ — Gain (loss) on sale of accounts receivable (a) (9.3 ) 9.0 (0.3 ) (5.0 ) 4.7 (0.6 ) Servicing fees received (paid) 1.2 (1.2 ) — 0.6 (0.6 ) — Fees paid to outside investor — (0.6 ) (0.6 ) — (0.3 ) (0.9 ) Cash from customers (transferred) received (715.8 ) 715.8 — (377.3 ) 377.3 — Cash received from (paid for) receivables purchased 706.8 (706.8 ) — 372.6 (372.6 ) — Interest on intercompany note received (paid) 0.1 (0.1 ) — — — —

Nuclear Plant (Tables)

Nuclear Plant (Tables)	6 Months Ended
	Jun. 30, 2015
Nuclear Plant [Abstract]
Changes in nuclear decommissioning trust fund	The following table summarizes the change in Great Plains Energy's and KCP&L's nuclear decommissioning trust fund. June 30 December 31 Decommissioning Trust (millions) Beginning balance January 1 $ 199.0 $ 183.9 Contributions 1.6 3.3 Earned income, net of fees 1.5 3.6 Net realized gains 0.8 0.4 Net unrealized gains 0.4 7.8 Ending balance $ 203.3 $ 199.0
Detail of assets held in nuclear decommissioning trust fund	The nuclear decommissioning trust is reported at fair value on the balance sheets and is invested in assets as detailed in the following table. June 30, 2015 December 31, 2014 Cost Basis Unrealized Gains Unrealized Losses Fair Value Cost Basis Unrealized Gains Unrealized Losses Fair Value (millions) Equity securities $ 88.5 $ 52.2 $ (0.6 ) $ 140.1 $ 87.2 $ 50.6 $ (0.7 ) $ 137.1 Debt securities 57.9 2.8 (0.4 ) 60.3 55.4 3.8 (0.1 ) 59.1 Other 2.9 — — 2.9 2.8 — — 2.8 Total $ 149.3 $ 55.0 $ (1.0 ) $ 203.3 $ 145.4 $ 54.4 $ (0.8 ) $ 199.0
Gains and losses from the sale of securities by the nuclear decommissioning trust fund	The following table summarizes the realized gains and losses from the sale of securities in the nuclear decommissioning trust fund. Three Months Ended Year to Date 2015 2014 2015 2014 (millions) Realized gains $ 1.2 $ 0.5 $ 2.6 $ 0.7 Realized losses (1.2 ) (0.5 ) (1.8 ) (0.6 )

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	6 Months Ended
	Jun. 30, 2015
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Change in Asset Retirement Obligation [Table Text Block]	The following table summarizes the change in Great Plains Energy's and KCP&L's AROs. Great Plains Energy KCP&L June 30 December 31 June 30 December 31 2015 2014 2015 2014 (millions) Beginning balance $ 195.9 $ 158.8 $ 177.7 $ 141.7 Additions 54.5 — 34.6 — Revision in timing and/or estimates 15.0 26.8 16.7 26.8 Accretion 6.1 10.3 5.6 9.2 Ending balance $ 271.5 $ 195.9 $ 234.6 $ 177.7

Pension Plans and Other Emplo32

Pension Plans and Other Employee Benefits (Tables)	6 Months Ended
	Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Schedule of Net Benefit Costs [Table Text Block]	The following tables provides Great Plains Energy's components of net periodic benefit costs prior to the effects of capitalization and sharing with joint owners of power plants. Pension Benefits Other Benefits Three Months Ended June 30 2015 2014 2015 2014 Components of net periodic benefit costs (millions) Service cost $ 11.3 $ 9.0 $ 0.9 $ 0.9 Interest cost 12.6 12.7 1.7 2.0 Expected return on plan assets (12.9 ) (12.7 ) (0.8 ) (0.7 ) Prior service cost 0.2 0.2 0.8 0.8 Recognized net actuarial loss 12.8 12.4 0.1 — Transition obligation — — — 0.1 Net periodic benefit costs before regulatory adjustment 24.0 21.6 2.7 3.1 Regulatory adjustment (2.6 ) (0.4 ) 1.4 1.1 Net periodic benefit costs $ 21.4 $ 21.2 $ 4.1 $ 4.2 Pension Benefits Other Benefits Year to Date June 30 2015 2014 2015 2014 Components of net periodic benefit costs (millions) Service cost $ 22.6 $ 18.1 $ 1.7 $ 1.8 Interest cost 25.2 25.4 3.4 4.0 Expected return on plan assets (25.8 ) (25.4 ) (1.5 ) (1.4 ) Prior service cost 0.4 0.4 1.6 1.6 Recognized net actuarial loss 25.6 24.8 0.1 — Transition obligation — — — 0.1 Net periodic benefit costs before regulatory adjustment 48.0 43.3 5.3 6.1 Regulatory adjustment (5.8 ) (0.8 ) 2.8 2.2 Net periodic benefit costs $ 42.2 $ 42.5 $ 8.1 $ 8.3

Equity Compensation (Tables)

Equity Compensation (Tables)	6 Months Ended
	Jun. 30, 2015
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Equity compensation expense and associated income tax benefits	The following table summarizes Great Plains Energy's and KCP&L's equity compensation expense and the associated income tax benefit. Three Months Ended Year to Date 2015 2014 2015 2014 Great Plains Energy (millions) Equity compensation expense $ 1.1 $ 1.0 $ 0.9 $ 5.4 Income tax benefit 0.3 0.3 0.3 2.0 KCP&L Equity compensation expense $ 0.7 $ 0.7 $ 0.6 $ 3.8 Income tax benefit 0.2 0.3 0.2 1.4
Performance share activity	Performance Shares Grant Date Fair Value* Beginning balance January 1, 2015 534,016 $ 25.11 Granted 228,049 24.06 Earned (25,844 ) 19.48 Performance adjustment (77,515 ) 19.48 Ending balance June 30, 2015 658,706 25.63 * weighted-average
Restricted stock activity	Nonvested Restricted Stock Grant Date Fair Value* Beginning balance January 1, 2015 267,390 $ 22.31 Granted and issued 77,937 26.18 Vested (103,861 ) 19.77 Ending balance June 30, 2015 241,466 24.65 * weighted-average

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Schedule of Debt [Table Text Block]	Great Plains Energy's and KCP&L's long-term debt is detailed in the following table. June 30 December 31 Year Due 2015 2014 KCP&L (millions) General Mortgage Bonds 2.83% EIRR bonds (a) 2017-2035 $ 132.4 $ 146.4 7.15% Series 2009A (8.59% rate) (b) 2019 400.0 400.0 4.65% EIRR Series 2005 2035 50.0 50.0 Senior Notes 5.85% Series (5.72% rate) (b) 2017 250.0 250.0 6.375% Series (7.49% rate) (b) 2018 350.0 350.0 3.15% Series 2023 300.0 300.0 6.05% Series (5.78% rate) (b) 2035 250.0 250.0 5.30% Series 2041 400.0 400.0 EIRR Bonds 0.08% Series 2007A and 2007B (c) 2035 146.5 146.5 2.875% Series 2008 2038 23.4 23.4 Current maturities — (14.0 ) Unamortized discount (3.7 ) (3.8 ) Total KCP&L excluding current maturities 2,298.6 2,298.5 Other Great Plains Energy GMO First Mortgage Bonds 9.44% Series 2016-2021 6.8 7.9 GMO Senior Notes 8.27% Series 2021 80.9 80.9 3.49% Series A 2025 125.0 125.0 4.06% Series B 2033 75.0 75.0 4.74% Series C 2043 150.0 150.0 GMO Medium Term Notes 7.33% Series 2023 3.0 3.0 7.17% Series 2023 7.0 7.0 Great Plains Energy Senior Notes 6.875% Series (7.33% rate) (b) 2017 100.0 100.0 4.85% Series 2021 350.0 350.0 5.292% Series 2022 287.5 287.5 Current maturities (1.1 ) (1.1 ) Unamortized discount and premium, net 4.0 4.3 Total Great Plains Energy excluding current maturities $ 3,486.7 $ 3,488.0 (a) Weighted-average interest rates at June 30, 2015 (b) Rate after amortizing gains/losses recognized in OCI on settlements of interest rate hedging instruments (c) Variable rate

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule Of Environmental Capital Expenditures [Table Text Block]	2015 2016 2017 2018 2019 (millions) Great Plains Energy $ 119.1 $ 62.2 $ 158.4 $ 103.4 $ 99.9 KCP&L 104.5 51.5 132.9 86.9 84.3

Related Party Transactions an36

Related Party Transactions and Relationships (Tables)	6 Months Ended
	Jun. 30, 2015
Related Party Transactions [Abstract]
Schedule of related party receivables and payables [Table Text Block]	The following table summarizes KCP&L's related party net receivables. June 30 December 31 2015 2014 (millions) Net receivable from GMO $ 33.8 $ 38.2 Net receivable from Great Plains Energy 20.3 18.0

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Values of open positions for derivative instruments [Table Text Block]	The gross notional contract amount and recorded fair values of open positions for derivative instruments are summarized in the following table. The fair values of these derivatives are recorded on the consolidated balance sheets. The fair values below are gross values before netting agreements and netting of cash collateral. June 30 December 31 2015 2014 Notional Contract Amount Fair Value Notional Contract Amount Fair Value Great Plains Energy (millions) Futures contracts Non-hedging derivatives $ 34.1 $ (2.9 ) $ 14.9 $ (2.4 ) Forward contracts Non-hedging derivatives 23.4 3.8 29.7 4.1 Transmission congestion rights Non-hedging derivatives 12.8 0.1 28.3 2.6 Option contracts Non-hedging derivatives — — 1.7 0.1 KCP&L Futures contracts Non-hedging derivatives $ 5.4 $ — $ — $ — Transmission congestion rights Non-hedging derivatives 9.5 0.1 23.6 3.1
Fair value of open derivative positions, gross values before netting agreements and netting of cash collatral [Table Text Block]	The fair values of Great Plains Energy's and KCP&L's open derivative positions and balance sheet classification are summarized in the following tables. The fair values below are gross values before netting agreements and netting of cash collateral. Great Plains Energy Balance Sheet Asset Derivatives Liability Derivatives June 30, 2015 Classification Fair Value Fair Value Derivatives Not Designated as Hedging Instruments (millions) Commodity contracts Other $ 4.4 $ 3.4 December 31, 2014 Derivatives Not Designated as Hedging Instruments Commodity contracts Other $ 8.6 $ 4.2 KCP&L Balance Sheet Asset Derivatives Liability Derivatives June 30, 2015 Classification Fair Value Fair Value Derivatives Not Designated as Hedging Instruments (millions) Commodity contracts Other $ 0.5 $ 0.4 December 31, 2014 Derivatives Not Designated as Hedging Instruments Commodity contracts Other $ 4.0 $ 0.9
Offsetting Derivative Assets and Liabilities [Table Text Block]	The following tables provide information regarding Great Plains Energy's and KCP&L's offsetting of derivative assets and liabilities. Great Plains Energy Gross Amounts Not Offset in the Statement of Financial Position Description Gross Amounts Recognized Gross Amounts Offset in the Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Financial Instruments Cash Collateral Net Amount June 30, 2015 (millions) Derivative assets $ 4.4 $ (0.5 ) $ 3.9 $ — $ — $ 3.9 Derivative liabilities 3.4 (3.3 ) 0.1 — — 0.1 December 31, 2014 Derivative assets $ 8.6 $ (1.2 ) $ 7.4 $ — $ — $ 7.4 Derivative liabilities 4.2 (3.5 ) 0.7 — — 0.7 KCP&L Gross Amounts Not Offset in the Statement of Financial Position Description Gross Amounts Recognized Gross Amounts Offset in the Statement of Financial Position Net Amounts Presented in the Statement of Financial Position Financial Instruments Cash Collateral Net Amount June 30, 2015 (millions) Derivative assets $ 0.5 $ (0.4 ) $ 0.1 $ — $ — $ 0.1 Derivative liabilities 0.4 (0.4 ) — — — — December 31, 2014 Derivative assets $ 4.0 $ (0.9 ) $ 3.1 $ — $ — $ 3.1 Derivative liabilities 0.9 (0.9 ) — — — —
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location [Table Text Block]	The following tables summarize the amounts of gain (loss) recognized for the change in fair value of commodity contract derivatives not designated as hedging instruments for Great Plains Energy and KCP&L. Great Plains Energy Three Months Ended Year to Date Derivatives Not Designated as Hedging Instruments 2015 2014 2015 2014 Location of Gain (Loss) (millions) Electric revenues $ (2.5 ) $ (3.2 ) $ (7.7 ) $ (2.3 ) Fuel (0.6 ) 0.6 (1.1 ) 1.0 Purchased power (1.1 ) — (1.2 ) 0.4 Regulatory asset 3.1 (4.0 ) (3.2 ) (4.1 ) Regulatory liability — (0.9 ) — 0.2 Total $ (1.1 ) $ (7.5 ) $ (13.2 ) $ (4.8 ) KCP&L Three Months Ended Year to Date Derivatives Not Designated as Hedging Instruments 2015 2014 2015 2014 Location of Gain (Loss) (millions) Electric revenues $ (2.5 ) $ (3.2 ) $ (7.7 ) $ (2.3 ) Fuel — 0.1 0.2 0.1 Regulatory asset 1.4 (2.1 ) — (2.2 ) Total $ (1.1 ) $ (5.2 ) $ (7.5 ) $ (4.4 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2015
Fair Value Disclosures [Abstract]
Fair value of assets and liabilities	The following tables include Great Plains Energy's and KCP&L's balances of financial assets and liabilities measured at fair value on a recurring basis. The fair values below are gross values before netting arrangements and netting of cash collateral. Description June 30 Level 1 Level 2 Level 3 KCP&L (millions) Assets Nuclear decommissioning trust (a) Equity securities $ 140.1 $ 140.1 $ — $ — Debt securities U.S. Treasury 24.9 24.9 — — U.S. Agency 2.1 — 2.1 — State and local obligations 4.0 — 4.0 — Corporate bonds 28.8 — 28.8 — Foreign governments 0.5 — 0.5 — Cash equivalents 2.9 2.9 — — Total nuclear decommissioning trust 203.3 167.9 35.4 — Self-insured health plan trust (b) Equity securities 1.2 1.2 — — Debt securities 7.2 — 7.2 — Cash and cash equivalents 7.4 7.4 — — Total self-insured health plan trust 15.8 8.6 7.2 — Derivative instruments (c) 0.5 0.1 — 0.4 Total $ 219.6 $ 176.6 $ 42.6 $ 0.4 Liabilities Derivative instruments (c) 0.4 0.1 — 0.3 Total $ 0.4 $ 0.1 $ — $ 0.3 Other Great Plains Energy Assets Derivative instruments (c) $ 3.9 $ — $ 3.1 $ 0.8 SERP rabbi trusts (d) Equity securities 0.1 0.1 — — Fixed income funds 17.3 — 17.3 — Total SERP rabbi trusts 17.4 0.1 17.3 — Total 21.3 0.1 20.4 0.8 Liabilities Derivative instruments (c) 3.0 2.9 — 0.1 Total $ 3.0 $ 2.9 $ — $ 0.1 Great Plains Energy Assets Nuclear decommissioning trust (a) $ 203.3 $ 167.9 $ 35.4 $ — Self-insured health plan trust (b) 15.8 8.6 7.2 — Derivative instruments (c) 4.4 0.1 3.1 1.2 SERP rabbi trusts (d) 17.4 0.1 17.3 — Total 240.9 176.7 63.0 1.2 Liabilities Derivative instruments (c) 3.4 3.0 — 0.4 Total $ 3.4 $ 3.0 $ — $ 0.4 Description December 31 Level 1 Level 2 Level 3 KCP&L (millions) Assets Nuclear decommissioning trust (a) Equity securities $ 137.1 $ 137.1 $ — $ — Debt securities U.S. Treasury 22.9 22.9 — — U.S. Agency 3.5 — 3.5 — State and local obligations 4.1 — 4.1 — Corporate bonds 28.1 — 28.1 — Foreign governments 0.5 — 0.5 — Cash equivalents 2.3 2.3 — — Other 0.5 — 0.5 — Total nuclear decommissioning trust 199.0 162.3 36.7 — Self-insured health plan trust (b) Equity securities 1.3 1.3 — — Debt securities 7.6 — 7.6 — Cash and cash equivalents 6.2 6.2 — — Total self-insured health plan trust 15.1 7.5 7.6 — Derivative instruments (c) 4.0 — — 4.0 Total $ 218.1 $ 169.8 $ 44.3 $ 4.0 Liabilities Derivative instruments (c) 0.9 — — 0.9 Total $ 0.9 $ — $ — $ 0.9 Other Great Plains Energy Assets Derivative instruments (c) $ 4.6 $ — $ 3.4 $ 1.2 SERP rabbi trusts (d) Equity securities 0.1 0.1 — — Fixed income funds 17.8 — 17.8 — Total SERP rabbi trusts 17.9 0.1 17.8 — Total 22.5 0.1 21.2 1.2 Liabilities Derivative instruments (c) 3.3 2.4 0.1 0.8 Total $ 3.3 $ 2.4 $ 0.1 $ 0.8 Great Plains Energy Assets Nuclear decommissioning trust (a) $ 199.0 $ 162.3 $ 36.7 $ — Self-insured health plan trust (b) 15.1 7.5 7.6 — Derivative instruments (c) 8.6 — 3.4 5.2 SERP rabbi trusts (d) 17.9 0.1 17.8 — Total 240.6 169.9 65.5 5.2 Liabilities Derivative instruments (c) 4.2 2.4 0.1 1.7 Total $ 4.2 $ 2.4 $ 0.1 $ 1.7 (a) Fair value is based on quoted market prices of the investments held by the fund and/or valuation models. (b) Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities. (c) The fair value of derivative instruments is estimated using market quotes, over-the-counter forward price and volatility curves and correlations among fuel prices, net of estimated credit risk. Derivative instruments classified as Level 1 represent exchange traded derivative instruments. Derivative instruments classified as Level 2 represent non-exchange traded derivative instruments traded in over-the-counter markets. Derivative instruments classified as Level 3 represent non-exchange traded derivatives traded in over-the-counter markets for which observable market data is not available to corroborate the valuation inputs and TCRs valued at the most recent auction price in the SPP Integrated Marketplace. (d) Fair value is based on quoted market prices for equity securities and Net Asset Value (NAV) per share for fixed income funds. The fixed income fund invests primarily in intermediate and long-term debt securities, can be redeemed immediately and is not subject to any restrictions on redemptions.
Unobservable inputs reconciliation	The following tables reconcile the beginning and ending balances for all Level 3 assets and liabilities measured at fair value on a recurring basis. Great Plains Energy Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset/(liability) at April 1 $ (1.2 ) $ 6.9 Total realized/unrealized gains (losses): included in electric revenue (2.5 ) (3.2 ) included in purchased power expense (1.1 ) — included in non-operating income 1.6 4.0 included in regulatory asset 2.0 (4.1 ) Purchases 0.4 7.3 Settlements 1.6 (10.3 ) Net asset at June 30 $ 0.8 $ 0.6 Total unrealized gains (losses) relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.4 ) included in non-operating income — 0.1 included in regulatory asset — (4.1 ) Great Plains Energy Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset at January 1 $ 3.5 $ 3.3 Total realized/unrealized gains (losses): included in electric revenue (7.7 ) (2.3 ) included in purchased power expense (1.2 ) 0.4 included in non-operating income 3.7 11.1 included in regulatory asset — (4.1 ) Purchases 0.6 13.4 Settlements 1.9 (21.2 ) Net asset at June 30 $ 0.8 $ 0.6 Total unrealized gains (losses) relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.5 ) included in non-operating income (0.1 ) 0.2 included in regulatory asset — (4.1 ) KCP&L Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset/(liability) at April 1 $ (0.8 ) $ 3.9 Total realized/unrealized gains (losses): included in electric revenue (2.5 ) (3.2 ) included in regulatory asset 1.4 (2.1 ) Purchases 0.2 6.7 Settlements 1.8 (4.4 ) Net asset at June 30 $ 0.1 $ 0.9 Total unrealized losses relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.4 ) included in regulatory asset — (2.1 ) KCP&L Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Derivative Instruments 2015 2014 (millions) Net asset at January 1 $ 3.1 $ 1.1 Total realized/unrealized gains (losses): included in electric revenue (7.7 ) (2.3 ) included in regulatory asset — (2.2 ) Purchases (0.2 ) 11.8 Settlements 4.9 (7.5 ) Net asset at June 30 $ 0.1 $ 0.9 Total unrealized losses relating to assets and liabilities still on the consolidated balance sheet at June 30: included in electric revenue $ — $ (2.5 ) included in regulatory asset — (2.2 )

Accumulated Other Comprehensi39

Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following tables reflect the change in the balances of each component of accumulated other comprehensive loss for Great Plains Energy and KCP&L. Great Plains Energy Gains and Losses on Cash Flow Hedges (a) Defined Benefit Pension Items (a) Total (a) (millions) Year to Date June 30, 2015 Beginning balance January 1 $ (15.8 ) $ (2.9 ) $ (18.7 ) Amounts reclassified from accumulated other comprehensive loss 2.8 0.3 3.1 Net current period other comprehensive income 2.8 0.3 3.1 Ending balance June 30 $ (13.0 ) $ (2.6 ) $ (15.6 ) Year to Date June 30, 2014 Beginning balance January 1 $ (23.8 ) $ (1.5 ) $ (25.3 ) Amounts reclassified from accumulated other comprehensive loss 5.3 0.2 5.5 Net current period other comprehensive income 5.3 0.2 5.5 Ending balance June 30 $ (18.5 ) $ (1.3 ) $ (19.8 ) (a) Net of tax KCP&L Gains and Losses on Cash Flow Hedges (a) (millions) Year to Date June 30, 2015 Beginning balance January 1 $ (14.9 ) Amounts reclassified from accumulated other comprehensive loss 2.7 Net current period other comprehensive income 2.7 Ending balance June 30 $ (12.2 ) Year to Date June 30, 2014 Beginning balance January 1 $ (20.2 ) Amounts reclassified from accumulated other comprehensive loss 2.7 Net current period other comprehensive income 2.7 Ending balance June 30 $ (17.5 ) (a) Net of tax
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following tables reflect the effect on certain line items of net income from amounts reclassified out of each component of accumulated other comprehensive loss for Great Plains Energy and KCP&L. Great Plains Energy Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Three Months Ended June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (2.3 ) $ (3.9 ) Interest charges (2.3 ) (3.9 ) Income before income tax expense and income from equity investments 0.9 1.4 Income tax benefit $ (1.4 ) $ (2.5 ) Net income Amortization of defined benefit pension items Net losses included in net periodic benefit costs $ (0.2 ) $ (0.1 ) Utility operating and maintenance expenses (0.2 ) (0.1 ) Income before income tax expense and income from equity investments — 0.1 Income tax benefit $ (0.2 ) $ — Net income Total reclassifications, net of tax $ (1.6 ) $ (2.5 ) Net income Great Plains Energy Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Year to Date June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (4.6 ) $ (8.6 ) Interest charges (4.6 ) (8.6 ) Income before income tax expense and income from equity investments 1.8 3.3 Income tax benefit $ (2.8 ) $ (5.3 ) Net income Amortization of defined benefit pension items Net losses included in net periodic benefit costs $ (0.4 ) $ (0.3 ) Utility operating and maintenance expenses (0.4 ) (0.3 ) Income before income tax expense and income from equity investments 0.1 0.1 Income tax benefit $ (0.3 ) $ (0.2 ) Net income Total reclassifications, net of tax $ (3.1 ) $ (5.5 ) Net income KCP&L Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Three Months Ended June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (2.1 ) $ (2.2 ) Interest charges (2.1 ) (2.2 ) Income before income tax expense 0.8 0.8 Income tax benefit Total reclassifications, net of tax $ (1.3 ) $ (1.4 ) Net income KCP&L Details about Accumulated Other Comprehensive Loss Components Amount Reclassified from Accumulated Other Comprehensive Loss Affected Line Item in the Income Statement Year to Date June 30 2015 2014 (millions) Gains and (losses) on cash flow hedges (effective portion) Interest rate contracts $ (4.4 ) $ (4.4 ) Interest charges (4.4 ) (4.4 ) Income before income tax expense 1.7 1.7 Income tax benefit Total reclassifications, net of tax $ (2.7 ) $ (2.7 ) Net income

Taxes (Tables)

Taxes (Tables)	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Components of income tax expense are detailed in the following tables. Three Months Ended Year to Date Great Plains Energy 2015 2014 2015 2014 Current income taxes (millions) Federal $ — $ (0.2 ) $ 0.5 $ 0.1 State — — (0.1 ) 0.1 Total — (0.2 ) 0.4 0.2 Deferred income taxes Federal 20.3 25.0 25.4 31.6 State 4.5 5.1 5.9 6.8 Total 24.8 30.1 31.3 38.4 Noncurrent income taxes Federal — (2.4 ) — (2.4 ) State — (0.3 ) — (0.3 ) Foreign — 0.2 — — Total — (2.5 ) — (2.7 ) Investment tax credit amortization (0.3 ) (0.4 ) (0.7 ) (0.8 ) Income tax expense $ 24.5 $ 27.0 $ 31.0 $ 35.1 Three Months Ended Year to Date KCP&L 2015 2014 2015 2014 Current income taxes (millions) Federal $ 4.2 $ (2.0 ) $ (1.5 ) $ 0.7 State 0.7 (0.3 ) (0.4 ) 0.2 Total 4.9 (2.3 ) (1.9 ) 0.9 Deferred income taxes Federal 7.9 14.9 16.2 15.3 State 2.4 3.3 4.4 3.9 Total 10.3 18.2 20.6 19.2 Investment tax credit amortization (0.3 ) (0.3 ) (0.5 ) (0.5 ) Income tax expense $ 14.9 $ 15.6 $ 18.2 $ 19.6
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Three Months Ended Year to Date Great Plains Energy 2015 2014 2015 2014 Federal statutory income tax rate 35.0 % 35.0 % 35.0 % 35.0 % Differences between book and tax depreciation not normalized 1.3 (0.6 ) 0.8 (0.9 ) Amortization of investment tax credits (0.5 ) (0.5 ) (0.8 ) (0.7 ) Federal income tax credits (4.0 ) (3.8 ) (5.6 ) (5.4 ) State income taxes 3.8 3.8 3.7 3.8 Changes in uncertain tax positions, net — 0.3 — — Other (0.1 ) (0.2 ) (0.3 ) (0.3 ) Effective income tax rate 35.5 % 34.0 % 32.8 % 31.5 % Three Months Ended Year to Date KCP&L 2015 2014 2015 2014 Federal statutory income tax rate 35.0 % 35.0 % 35.0 % 35.0 % Differences between book and tax depreciation not normalized 2.0 (0.9 ) 1.3 (1.8 ) Amortization of investment tax credits (0.6 ) (0.5 ) (0.9 ) (0.7 ) Federal income tax credits (6.2 ) (5.9 ) (8.7 ) (8.3 ) State income taxes 4.1 3.8 4.0 3.7 Other (0.6 ) (0.5 ) (0.7 ) (0.6 ) Effective income tax rate 33.7 % 31.0 % 30.0 % 27.3 %

Segments and Related Informat41

Segments and Related Information (Tables)	6 Months Ended
	Jun. 30, 2015
Segment Reporting [Abstract]
Segment Financial Information [Table Text Block]	Three Months Ended June 30, 2015 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 609.0 $ — $ — $ 609.0 Depreciation and amortization (83.5 ) — — (83.5 ) Interest (charges) income (47.9 ) (10.1 ) 8.0 (50.0 ) Income tax (expense) benefit (25.6 ) 1.1 — (24.5 ) Net income (loss) 46.4 (2.0 ) — 44.4 Year to Date June 30, 2015 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 1,158.1 $ — $ — $ 1,158.1 Depreciation and amortization (163.3 ) — — (163.3 ) Interest (charges) income (93.2 ) (20.1 ) 16.0 (97.3 ) Income tax (expense) benefit (33.5 ) 2.5 — (31.0 ) Net income (loss) 67.3 (4.0 ) — 63.3 Three Months Ended June 30, 2014 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 648.4 $ — $ — $ 648.4 Depreciation and amortization (75.6 ) — — (75.6 ) Interest (charges) income (46.0 ) (11.7 ) 9.4 (48.3 ) Income tax (expense) benefit (28.0 ) 1.0 — (27.0 ) Net income (loss) 54.7 (2.6 ) — 52.1 Year to Date June 30, 2014 Electric Utility Other Eliminations Great Plains Energy (millions) Operating revenues $ 1,233.5 $ — $ — $ 1,233.5 Depreciation and amortization (150.1 ) — — (150.1 ) Interest (charges) income (93.0 ) (24.3 ) 19.6 (97.7 ) Income tax (expense) benefit (37.8 ) 2.7 — (35.1 ) Net income (loss) 80.8 (4.9 ) — 75.9 Electric Utility Other Eliminations Great Plains Energy June 30, 2015 (millions) Assets $ 11,039.4 $ 126.1 $ (403.3 ) $ 10,762.2 Capital expenditures (a) 366.8 — — 366.8 December 31, 2014 Assets $ 10,746.1 $ 33.1 $ (303.5 ) $ 10,475.7 Capital expenditures (a) 773.7 — — 773.7

Summary of Significant Accoun42

Summary of Significant Accounting Policies Equity Method Investment (Details) - Jun. 30, 2015 - Transource Energy, LLC [Member]	Total
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Description of Principal Activities	Transource is focused on the development of competitive electric transmission projects.
GPE Transmission Holding Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	13.50%
AEP Transmission Holding Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage of Majority Owner	86.50%

Summary of Significant Accoun43

Summary of Significant Accounting Policies Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ 44.4	$ 52.1	$ 63.3	$ 75.9
Income [Abstract]
Less: preferred stock dividend requirements	0.4	0.4	0.8	0.8
Earnings (loss) available for common shareholders	$ 44	$ 51.7	$ 62.5	$ 75.1
Common Shares Outstanding [Abstract]
Average number of common shares outstanding (in shares)	154.1	153.8	154.1	153.8
Add: effect of dilutive securities (in shares)	0.4	0.2	0.4	0.2
Diluted average number of common shares outstanding (in shares)	154.5	154	154.5	154
Earnings Per Share [Abstract]
Earnings Per Share, Basic and Diluted	$ 0.28	$ 0.34	$ 0.40	$ 0.49

Summary of Significant Accoun44

Summary of Significant Accounting Policies Antidilutive Securities (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	475,549	0	475,549
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0	0	287

Summary of Significant Accoun45

Summary of Significant Accounting Policies Subsequent Events (Details) - Aug. 31, 2015 - Subsequent Event [Member] - $ / shares	Total
Common Stock [Member]
Dividends Declared [Abstract]
Dividends Payable, Date Declared, Month and Year	2015-08
Dividends Payable, Amount Per Share	$ 0.245
Dividends Payable, Date to be Paid	Sep. 21, 2015
Dividends Payable, Date of Record	Aug. 28, 2015
Preferred Stock [Member]
Dividends Declared [Abstract]
Dividends Payable, Date Declared, Month and Year	2015-08
Dividends Payable, Date to be Paid	Dec. 1, 2015
Dividends Payable, Date of Record	Nov. 6, 2015

Supplemental Cash Flow Inform46

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows affected by changes in:
Receivables	$ (36)	$ (57.1)
Accounts receivable pledged as collateral	8	4
Fuel inventories	(12.2)	3.9
Materials and supplies	0.3	4.1
Accounts payable	(108.2)	(76.1)
Accrued taxes	47.5	46
Accrued interest	(1.3)	(1.3)
Deferred refueling outage costs	(17.7)	8.4
Pension and post-retirement benefit obligations	25	5.3
Allowance for equity funds used during construction	(3.5)	(9)
Fuel recovery mechanism	25.6	(17.3)
Solar rebates paid	(4.8)	(33.3)
Other operating activities	3.9	(5.5)
Total other operating activities	(73.4)	(127.9)
Cash paid during the period:
Interest Paid, Net	91.9	88.2
Income Taxes Paid	0.2	0.1
Non-cash investing activities:
Liabilities accrued for capital expenditures	34.8	46.7
Kansas City Power and Light Company [Member]
Cash flows affected by changes in:
Receivables	(1.4)	(34.4)
Fuel inventories	(11.9)	6.6
Materials and supplies	0.1	2.8
Accounts payable	(69.7)	(38.8)
Accrued taxes	94.4	31.9
Accrued interest	(1.5)	(1.5)
Deferred refueling outage costs	(17.7)	8.4
Pension and post-retirement benefit obligations	25.1	4.4
Allowance for equity funds used during construction	(2.7)	(8.5)
Fuel recovery mechanism	0.6	2.4
Solar rebates paid	(4.1)	(10.7)
Other operating activities	3.7	(15.8)
Total other operating activities	14.9	(53.2)
Cash paid during the period:
Interest Paid, Net	61.2	57.2
Non-cash investing activities:
Liabilities accrued for capital expenditures	$ 31.4	$ 39.3

Receivables (Details)

Receivables (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased		$ 0	$ 0	$ 0	$ 0
Gain (Loss) on Sale of Accounts Receivable	[1]	(0.6)	(0.7)	(0.5)	(0.6)
Servicing fees received (paid)		0	0	0	0
Fees paid to outside investor		(0.3)	(0.4)	(0.6)	(0.9)
Cash from customers (transferred) received		0	0	0	0
Cash received from (paid for) receivables purchased		0	0	0	0
Interest on intercompany note received (paid)		0	0	0	0
Kansas City Power and Light Company [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased		0	0	0	0
Gain (Loss) on Sale of Accounts Receivable	[1]	(0.4)	(0.4)	(0.3)	(0.3)
Servicing fees received (paid)		0	0	0	0
Fees paid to outside investor		(0.2)	(0.3)	(0.4)	(0.6)
Cash from customers (transferred) received		0	0	0	0
Cash received from (paid for) receivables purchased		0	0	0	0
Interest on intercompany note received (paid)		0	0	0	0
Kansas City Power And Light Company Unconsolidated [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased		(388.7)	(380.9)	(738.5)	(734)
Gain (Loss) on Sale of Accounts Receivable	[1]	(4.9)	(4.8)	(9.3)	(9.3)
Servicing fees received (paid)		0.6	0.6	1.2	1.2
Fees paid to outside investor		0	0	0	0
Cash from customers (transferred) received		(356.3)	(348.2)	(716.1)	(715.8)
Cash received from (paid for) receivables purchased		351.8	343.8	707.1	706.8
Interest on intercompany note received (paid)		0	0.1	0.1	0.1
KCPL Receivables Company [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased		388.7	380.9	738.5	734
Gain (Loss) on Sale of Accounts Receivable	[1]	4.5	4.4	9	9
Servicing fees received (paid)		(0.6)	(0.6)	(1.2)	(1.2)
Fees paid to outside investor		(0.2)	(0.3)	(0.4)	(0.6)
Cash from customers (transferred) received		356.3	348.2	716.1	715.8
Cash received from (paid for) receivables purchased		(351.8)	(343.8)	(707.1)	(706.8)
Interest on intercompany note received (paid)		0	(0.1)	(0.1)	(0.1)
KCPL Greater Missouri Operations [Member]
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased		(200.6)	(197.9)	(389.3)	(391.7)
Gain (Loss) on Sale of Accounts Receivable	[1]	(2.5)	(2.5)	(4.9)	(5)
Servicing fees received (paid)		0.3	0.3	0.6	0.6
Fees paid to outside investor		0	0	0	0
Cash from customers (transferred) received		(183.5)	(176.5)	(378.3)	(377.3)
Cash received from (paid for) receivables purchased		181.3	174.3	373.6	372.6
Interest on intercompany note received (paid)		0.1	0	0.1	0
GMO Receivables Company Member
Accounts Receivable Sold [Line Items]
Receivables (sold) purchased		200.6	197.9	389.3	391.7
Gain (Loss) on Sale of Accounts Receivable	[1]	2.3	2.2	4.7	4.7
Servicing fees received (paid)		(0.3)	(0.3)	(0.6)	(0.6)
Fees paid to outside investor		(0.1)	(0.1)	(0.2)	(0.3)
Cash from customers (transferred) received		183.5	176.5	378.3	377.3
Cash received from (paid for) receivables purchased		(181.3)	(174.3)	(373.6)	(372.6)
Interest on intercompany note received (paid)		$ (0.1)	$ 0	$ (0.1)	$ 0
[1]	Any net gain (loss) is the result of the timing difference inherent in collecting receivables and over the life of the agreement will net to zero.

Receivables Accounts, Notes, an

Receivables Accounts, Notes, and Financing (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Receivables, Gross, Current	$ 75.1	$ 86.7
Receivables, net	196.2	160.3
Kansas City Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other Receivables, Gross, Current	69.3	79.8
Receivables, net	144.9	128.9
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts	(5.3)	(2.8)
Trade Accounts Receivable [Member] | Kansas City Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for doubtful accounts	(2.8)	(1.2)
Trade Accounts Receivable [Member] | Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	3.2	1.1
Trade Accounts Receivable [Member] | Billed Revenues [Member] | Kansas City Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	1.1	0.6
Trade Accounts Receivable [Member] | Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	123.2	75.3
Trade Accounts Receivable [Member] | Unbilled Revenues [Member] | Kansas City Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	$ 77.3	$ 49.7

Receivables Narrative (Details)

Receivables Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Accounts receivable pledged as collateral	$ 163	$ 171
Collateralized note payable	163	171
Kansas City Power and Light Company [Member]
Accounts receivable pledged as collateral	110	110
Collateralized note payable	$ 110	$ 110
Contractually Specified Servicing Fees Percentage Amount	1.50%
Maximum amount of outstanding principal under receivables agreement	$ 110
KCPL Greater Missouri Operations [Member]
Contractually Specified Servicing Fees Percentage Amount	1.50%
Maximum amount of outstanding principal under receivables agreement from mid-June 2015 through September 2015	$ 80
Maximum amount of outstanding principal under receivables agreement from mid-November 2014 to mid-June 2015	$ 65

Nuclear Plant (Details)

Nuclear Plant (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Investments in decommissioning trust fund [Line Items]
Cost Basis	$ 149.3		$ 149.3		$ 145.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	55		55		54.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1)		(1)		(0.8)
Fair Value, Nuclear decommissioning trust fund	203.3		$ 203.3		199	$ 183.9
Weighted average maturity of debt securities (in years)			7 years
Realized gains on investments in decommissioning trust fund	1.2	$ 0.5	$ 2.6	$ 0.7
Realized losses on investments in decommissioning trust fund	(1.2)	$ (0.5)	(1.8)	$ (0.6)
Equity Securities [Member]
Investments in decommissioning trust fund [Line Items]
Cost Basis	88.5		88.5		87.2
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	52.2		52.2		50.6
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	(0.6)		(0.6)		(0.7)
Fair Value, Nuclear decommissioning trust fund	140.1		140.1		137.1
Debt Securities [Member]
Investments in decommissioning trust fund [Line Items]
Cost Basis	57.9		57.9		55.4
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	2.8		2.8		3.8
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(0.4)		(0.4)		(0.1)
Fair Value, Nuclear decommissioning trust fund	60.3		60.3		59.1
Other Securities [Member]
Investments in decommissioning trust fund [Line Items]
Cost Basis	2.9		2.9		2.8
Fair Value, Nuclear decommissioning trust fund	$ 2.9		$ 2.9		$ 2.8

Nuclear Plant Decommissioning T

Nuclear Plant Decommissioning Trust (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Nuclear decommissioning trust fund [Roll Forward]
Nuclear decommissioning trust fund, beginning balance	$ 199	$ 183.9
Contributions to nuclear decommissioning trust fund	1.6	3.3
Earned income, net of fees	1.5	3.6
Net realized gains (losses) on nuclear decommissioning trust fund	0.8	0.4
Net unrealized gains (losses) on nuclear decommissioning trust fund	0.4	7.8
Nuclear decommissioning trust fund, ending balance	$ 203.3	199
Wolf Creek [Member]
Nuclear Insurance [Abstract]
Ownership percentage in Wolf Creek, a nuclear generating unit (in hundredths)	47.00%
Kansas City Power and Light Company [Member]
Nuclear decommissioning trust fund [Roll Forward]
Nuclear decommissioning trust fund, beginning balance	$ 199	183.9
Contributions to nuclear decommissioning trust fund	1.6	3.3
Earned income, net of fees	1.5	3.6
Net realized gains (losses) on nuclear decommissioning trust fund	0.8	0.4
Net unrealized gains (losses) on nuclear decommissioning trust fund	0.4	7.8
Nuclear decommissioning trust fund, ending balance	$ 203.3	$ 199
Kansas City Power and Light Company [Member] | Wolf Creek [Member]
Nuclear Insurance [Abstract]
Ownership percentage in Wolf Creek, a nuclear generating unit (in hundredths)	47.00%

Regulatory Matters (Details)

Regulatory Matters (Details) - Kansas City Power and Light Company [Member] - USD ($) $ in Millions	1 Months Ended
	May. 31, 2015	Jan. 31, 2015	Oct. 31, 2014
Missouri Public Service Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase, requested			$ 120.9
Return on equity, requested (in hundredths)			10.30%
Rate-making equity ratio, requested (in hundredths)			50.36%
Kansas Corporation Commission [Member]
Regulatory Proceedings [Line Items]
Annual revenue increase, requested		$ 67.3
Return on equity, requested (in hundredths)		10.30%
Rate-making equity ratio, requested (in hundredths)		50.48%
Commission Staff Recommended Return On Equity Percentage	9.25%
Commission Staff Recommended Rate Increase (Decrease) Amount	$ 44

Regulatory Matters Subsequent E

Regulatory Matters Subsequent Events (Details) - Kansas City Power and Light Company [Member] - USD ($) $ in Millions	1 Months Ended
	Jul. 31, 2015	May. 31, 2015	Jan. 31, 2015	Oct. 31, 2014
Kansas Corporation Commission [Member]
Subsequent Event [Line Items]
Annual revenue increase, requested			$ 67.3
Return on equity, requested (in hundredths)			10.30%
Rate-making equity ratio, requested (in hundredths)			50.48%
Staff recommended annual revenue increase		$ 44
Commission Staff Recommended Return On Equity Percentage		9.25%
Missouri Public Service Commission [Member]
Subsequent Event [Line Items]
Annual revenue increase, requested				$ 120.9
Return on equity, requested (in hundredths)				10.30%
Rate-making equity ratio, requested (in hundredths)				50.36%
Missouri Public Service Commission [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Annual revenue increase, requested	$ 112.7
Return on equity, requested (in hundredths)	10.30%
Missouri Public Service Commission [Member] | Subsequent Event [Member] | Maximum [Member]
Subsequent Event [Line Items]
Staff recommended annual revenue increase	$ 87.3
Commission Staff Recommended Return On Equity Percentage	9.50%
Missouri Public Service Commission [Member] | Subsequent Event [Member] | Minimum [Member]
Subsequent Event [Line Items]
Staff recommended annual revenue increase	$ 76.8
Commission Staff Recommended Return On Equity Percentage	9.00%

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Millions	Apr. 17, 2015	Jun. 30, 2015	Dec. 31, 2014
Increase in asset retirement obligations due to CCR regulations	$ 69.5
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance		$ 195.9	$ 158.8
Additions		54.5	0
Revision in timing and/or estimates		15	26.8
Accretion		6.1	10.3
Asset Retirement Obligation, Ending Balance		$ 271.5	195.9
Asset Retirement Obligations, Liability Not Recognized		certain wiring used in Great Plains Energy's and KCP&L's generating stations include asbestos insulation, which would require special handling if disturbed. Due to the inability to reasonably estimate the quantities or the amount of disturbance that will be necessary during dismantlement at the end of the life of a plant, the fair value of this ARO cannot be reasonably estimated at this time. Management will continue to monitor the obligation and will recognize a liability in the period in which sufficient information becomes available to reasonably estimate its fair value.
Kansas City Power and Light Company [Member]
Asset Retirement Obligations, Description		KCP&L has AROs related to decommissioning Wolf Creek, site remediation of its Spearville Wind Energy Facilities, asbestos abatement, removal of storage tanks and closure of ponds and landfills containing coal combustion residuals (CCRs).
Increase in asset retirement obligations due to CCR regulations	$ 51.3
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance		$ 177.7	141.7
Additions		34.6	0
Revision in timing and/or estimates		16.7	26.8
Accretion		5.6	9.2
Asset Retirement Obligation, Ending Balance		$ 234.6	$ 177.7
KCPL Greater Missouri Operations [Member]
Asset Retirement Obligations, Description		GMO has AROs related to asbestos abatement, removal of storage tanks and closure of ponds and landfills containing CCRs.

Pension Plans and Other Emplo55

Pension Plans and Other Employee Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer			$ 36.3
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			42.6
Components of net periodic benefit costs [Abstract]
Defined Benefit Plan, Service Cost	$ 11.3	$ 9	22.6	$ 18.1
Defined Benefit Plan, Interest Cost	12.6	12.7	25.2	25.4
Defined Benefit Plan, Expected Return on Plan Assets	(12.9)	(12.7)	(25.8)	(25.4)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.2	0.2	0.4	0.4
Defined Benefit Plan, Amortization of (Gains) Losses	12.8	12.4	25.6	24.8
Defined Benefit Plan, Amortization of Transition Obligations (Assets)	0	0	0	0
Net periodic benefit costs before regulatory adjustment	24	21.6	48	43.3
Defined benefit plan, regulatory adjustment	(2.6)	(0.4)	(5.8)	(0.8)
Defined Benefit Plan, Net Periodic Benefit Cost	21.4	21.2	42.2	42.5
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year			10.2
Components of net periodic benefit costs [Abstract]
Defined Benefit Plan, Service Cost	0.9	0.9	1.7	1.8
Defined Benefit Plan, Interest Cost	1.7	2	3.4	4
Defined Benefit Plan, Expected Return on Plan Assets	(0.8)	(0.7)	(1.5)	(1.4)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.8	0.8	1.6	1.6
Defined Benefit Plan, Amortization of (Gains) Losses	0.1	0	0.1	0
Defined Benefit Plan, Amortization of Transition Obligations (Assets)	0	0.1	0	0.1
Net periodic benefit costs before regulatory adjustment	2.7	3.1	5.3	6.1
Defined benefit plan, regulatory adjustment	1.4	1.1	2.8	2.2
Defined Benefit Plan, Net Periodic Benefit Cost	$ 4.1	$ 4.2	$ 8.1	$ 8.3
Wolf Creek [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	47.00%		47.00%
Wolf Creek [Member] | Kansas City Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	47.00%		47.00%

Equity Compensation (Details)

Equity Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity compensation expense		$ 1.1	$ 1	$ 0.9		$ 5.4
Income tax benefit		$ 0.3	$ 0.3	$ 0.3		$ 2
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility				16.00%
Expected dividend yield				3.72%
Risk-free interest rate				1.02%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)				534,016
Granted (in shares)		0	0	228,049
Earned (in shares)				(25,844)
Performance adjustment (in shares)				(77,515)
Ending balance (in shares)		658,706		658,706
Weighted average beginning balance (in dollars per share)	[1]			$ 25.11
Weighted average granted (in dollars per share)				24.06	[1]	$ 28.78
Weighted average earned (in dollars per share)	[1]			19.48
Weighted average performance adjustment (in dollars per share)	[1]			19.48
Weighted average ending balance (in dollars per share)	[1]	$ 25.63		$ 25.63
Total unrecognized compensation expense		$ 8.9		$ 8.9
Remaining weighted-average contractual term (in years)				01 year 6 months
Fair value of performance shares earned and paid				$ 0.5		$ 2.8
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)				267,390
Granted (in shares)		0		77,937
Vested (in shares)				(103,861)
Ending balance (in shares)		241,466		241,466
Weighted average beginning balance (in dollars per share)	[1]			$ 22.31
Weighted average granted (in dollars per share)			$ 25.54	26.18	[1]	$ 25.72
Weighted average vested (in dollars per share)	[1]			19.77
Weighted average ending balance (in dollars per share)	[1]	$ 24.65		$ 24.65
Total unrecognized compensation expense		$ 3.2		$ 3.2
Total fair value of shares vested		0.1	$ 0.2	$ 2		$ 1.5
Remaining weighted-average contractual term (in years)				01 year 8 months
Kansas City Power and Light Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity compensation expense		0.7	0.7	$ 0.6		3.8
Income tax benefit		$ 0.2	$ 0.3	$ 0.2		$ 1.4
[1]	weighted-average

Short-term Borrowings and Sho57

Short-term Borrowings and Short-term Bank Lines of Credit (Details) - USD ($)	1 Months Ended	6 Months Ended
	May. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Amount of outstanding cash borrowings		$ 11,000,000	$ 4,000,000
Commercial paper outstanding		629,300,000	358,300,000
Parent Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility		$ 200,000,000
Revolving credit facility expiration date		Oct. 31, 2019
Maximum borrowing capacity with transfer of unused commitments		$ 400,000,000
Line of Credit Facility, Covenant Terms		A default by Great Plains Energy or any of its significant subsidiaries on other indebtedness totaling more than $50.0 million is a default under the facility.  Under the terms of this facility, Great Plains Energy is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance		in compliance
Amount of outstanding cash borrowings		$ 11,000,000	$ 4,000,000
Weighted-average interest rate from outstanding borrowings		1.69%	1.69%
Amount of letters of credit outstanding		$ 200,000	$ 0
Kansas City Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial paper outstanding		$ 484,000,000	$ 358,300,000
Weighted-average interest rate from outstanding borrowings		0.49%	0.48%
Kansas City Power and Light Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility		$ 600,000,000
Revolving credit facility expiration date		Oct. 31, 2019
Maximum transfer of unused commitments		$ 200,000,000
Line Of Credit Facility Transfer Unused Commitments	$ 200,000,000
Line of Credit Facility, Covenant Terms		A default by KCP&L on other indebtedness totaling more than $50.0 million is a default under the facility.  Under the terms of this facility, KCP&L is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance		in compliance
Amount of outstanding cash borrowings		$ 0	$ 0
Amount of letters of credit outstanding		2,700,000	2,700,000
KCPL Greater Missouri Operations [Member]
Short-term Debt [Line Items]
Commercial paper outstanding		$ 145,300,000	0
Weighted-average interest rate from outstanding borrowings		0.45%
KCPL Greater Missouri Operations [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility		$ 450,000,000
Revolving credit facility expiration date		Oct. 31, 2019
Maximum transfer of unused commitments		$ 200,000,000
Line Of Credit Facility Transfer Unused Commitments	$ (50,000,000)
Line of Credit Facility, Covenant Terms		A default by GMO or any of its significant subsidiaries on other indebtedness totaling more than $50.0 million is a default under the facility.  Under the terms of this facility, GMO is required to maintain a consolidated indebtedness to consolidated capitalization ratio, as defined in the facility, not greater than 0.65 to 1.00 at all times.
Line of Credit Facility, Covenant Compliance		in compliance
Amount of outstanding cash borrowings		$ 0	0
Amount of letters of credit outstanding		$ 3,000,000	$ 3,200,000

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Millions		1 Months Ended	6 Months Ended
		Mar. 31, 2015	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Current maturities			$ (1.1)		$ (15.1)
Long-term debt excluding current maturities			3,486.7		3,488
Repayments of Long-term Debt			15.1	$ 13.4
Kansas City Power and Light Company [Member]
Debt Instrument [Line Items]
Current maturities			0		(14)
Unamortized discount			(3.7)		(3.8)
Long-term debt excluding current maturities			2,298.6		2,298.5
Repayments of Long-term Debt			14	$ 0
Kansas City Power and Light Company [Member] | Secured Debt [Member] | General Mortgage Bonds EIRR due 2017-2035 [Member]
Debt Instrument [Line Items]
Principal outstanding	[1]		$ 132.4		146.4
Debt Instrument Maturity Date Range Start			Dec. 31, 2017
Debt Instrument Maturity Date Range End			Dec. 31, 2035
Long-term Debt, Weighted Average Interest Rate			2.83%
Kansas City Power and Light Company [Member] | Secured Debt [Member] | General Mortgage bonds Series 2009A due 2019 [Member]
Debt Instrument [Line Items]
Principal outstanding	[2]		$ 400		400
Debt Instrument, Maturity Date			Dec. 31, 2019
Interest rates (in hundredths)			7.15%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)			8.59%
Kansas City Power and Light Company [Member] | Secured Debt [Member] | General Mortgage bonds EIRR series 2005 due 2035 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 50		50
Debt Instrument, Maturity Date			Dec. 31, 2035
Interest rates (in hundredths)			4.65%
Kansas City Power and Light Company [Member] | Secured Debt [Member] | Secured EIRR Bonds Series 2005 [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt		$ 14
Kansas City Power and Light Company [Member] | Senior Notes [Member] | Senior notes due 2017 KCPL [Member]
Debt Instrument [Line Items]
Principal outstanding	[2]		$ 250		250
Debt Instrument, Maturity Date			Dec. 31, 2017
Interest rates (in hundredths)			5.85%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)			5.72%
Kansas City Power and Light Company [Member] | Senior Notes [Member] | Senior notes due 2018 KCPL [Member]
Debt Instrument [Line Items]
Principal outstanding	[2]		$ 350		350
Debt Instrument, Maturity Date			Dec. 31, 2018
Interest rates (in hundredths)			6.375%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)			7.49%
Kansas City Power and Light Company [Member] | Senior Notes [Member] | Senior Notes due 2023 KCPL [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 300		300
Debt Instrument, Maturity Date			Dec. 31, 2023
Interest rates (in hundredths)			3.15%
Kansas City Power and Light Company [Member] | Senior Notes [Member] | Senior notes due 2035 KCPL [Member]
Debt Instrument [Line Items]
Principal outstanding	[2]		$ 250		250
Debt Instrument, Maturity Date			Dec. 31, 2035
Interest rates (in hundredths)			6.05%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)			5.78%
Kansas City Power and Light Company [Member] | Senior Notes [Member] | Senior Notes Due 2041 KCPL [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 400		400
Debt Instrument, Maturity Date			Dec. 31, 2041
Interest rates (in hundredths)			5.30%
Kansas City Power and Light Company [Member] | Unsecured Debt [Member] | EIRR Bonds Series 2007A and 2007B due 2035 [Member]
Debt Instrument [Line Items]
Principal outstanding	[3]		$ 146.5		146.5
Debt Instrument, Maturity Date			Dec. 31, 2035
Variable rate (in hundredths)			0.08%
Kansas City Power and Light Company [Member] | Unsecured Debt [Member] | EIRR bonds 2.875 percent Series 2008 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 23.4		23.4
Debt Instrument, Maturity Date			Dec. 31, 2038
Interest rates (in hundredths)			2.875%
KCPL Greater Missouri Operations [Member] | Secured Debt [Member] | First Mortgage Bonds due through 2021 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 6.8		7.9
Debt Instrument Maturity Date Range Start			Dec. 31, 2016
Debt Instrument Maturity Date Range End			Dec. 31, 2021
Interest rates (in hundredths)			9.44%
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior notes 8.27 percent series due 2021 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 80.9		80.9
Debt Instrument, Maturity Date			Dec. 31, 2021
Interest rates (in hundredths)			8.27%
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior Notes Series A due 2025 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 125		125
Debt Instrument, Maturity Date			Dec. 31, 2025
Interest rates (in hundredths)			3.49%
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior Notes Series B due 2033 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 75		75
Debt Instrument, Maturity Date			Dec. 31, 2033
Interest rates (in hundredths)			4.06%
KCPL Greater Missouri Operations [Member] | Senior Notes [Member] | Senior Notes Series C due 2043 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 150		150
Debt Instrument, Maturity Date			Dec. 31, 2043
Interest rates (in hundredths)			4.74%
KCPL Greater Missouri Operations [Member] | Medium-term Notes [Member] | Medium term notes 7.33 percent series due 2023 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 3		3
Debt Instrument, Maturity Date			Dec. 31, 2023
Interest rates (in hundredths)			7.33%
KCPL Greater Missouri Operations [Member] | Medium-term Notes [Member] | Medium term notes 7.17 percent series due 2023 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 7		7
Debt Instrument, Maturity Date			Dec. 31, 2023
Interest rates (in hundredths)			7.17%
Parent Company [Member] | Senior Notes [Member] | Senior notes due 2017 [Member]
Debt Instrument [Line Items]
Principal outstanding	[2]		$ 100		100
Debt Instrument, Maturity Date			Dec. 31, 2017
Interest rates (in hundredths)			6.875%
Rate after amortizing gains or losses in Other Comprehensive Income (in hundredths)			7.33%
Parent Company [Member] | Senior Notes [Member] | Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 350		350
Debt Instrument, Maturity Date			Dec. 31, 2021
Interest rates (in hundredths)			4.85%
Parent Company [Member] | Senior Notes [Member] | Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Principal outstanding			$ 287.5		287.5
Debt Instrument, Maturity Date			Dec. 31, 2022
Interest rates (in hundredths)			5.292%
Other Consolidated Entities [Member]
Debt Instrument [Line Items]
Current maturities			$ (1.1)		(1.1)
Unarmortized discount and premium, net			$ 4		$ 4.3
[1]	Weighted-average interest rates at June 30, 2015
[2]	Rate after amortizing gains/losses recognized in OCI on settlements of interest rate hedging instruments
[3]	Variable rate

Commitments and Contingencies E

Commitments and Contingencies Environmental Matters (Details) T in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2015USD ($)TMW	Dec. 31, 2014USD ($)
Estimated Environmental Capital Expenditures [Abstract]
Estimate Of Environmental Capital Expenditures Current	$ 119.1
Estimate Of Environmental Capital Expenditures In Two Years	62.2
Estimate Of Environmental Capital Expenditures In Three Years	158.4
Estimate Of Environmental Capital Expenditures In Four Years	103.4
Estimate Of Environmental Capital Expenditures In Five Years	$ 99.9
Mercury and Air Toxics Standards Rule [Abstract]
Capacity of electric steam generating units that fall under MACT standards (in megawatts) | MW	25
SO2 National Ambient Air Quality Standard (NAAQS) [Abstract]
Primary one-hour sulfur dioxide standard, as revised June 2010 (in parts per million)	0.075
Primary twenty-four hour sulfur dioxide standard, prior to June 2010 (in parts per million)	0.140
Primary one-year sulfur dioxide standard, prior to June 2010 (in parts per million)	0.030
Climate Change [Abstract]
CO2 produced per year (in tons) | T	22
EPA nationwide CO2 emission reductions by 2030	32.00%
Remediation [Abstract]
Accrued environmental remediation expenses	$ 1.4	$ 1.4
MISSOURI
Climate Change [Abstract]
EPA Interim Co2 Goal Rate Reduction	26.00%
EPA Co2 Emission Reductions By 2030 By State	37.00%
KANSAS
Climate Change [Abstract]
EPA Interim Co2 Goal Rate Reduction	34.00%
EPA Co2 Emission Reductions By 2030 By State	44.00%
LaCygne Station [Member]
Best Available Retrofit Technology Rule [Abstract]
Predetermination request for environmental equipment required at LaCygne Station to comply with BART	$ 1,230
Final expected amount below predetermination request for environmental upgrades at LaCynge Station to comply with BART	75
Kansas City Power and Light Company [Member]
Estimated Environmental Capital Expenditures [Abstract]
Estimate Of Environmental Capital Expenditures Current	104.5
Estimate Of Environmental Capital Expenditures In Two Years	51.5
Estimate Of Environmental Capital Expenditures In Three Years	132.9
Estimate Of Environmental Capital Expenditures In Four Years	86.9
Estimate Of Environmental Capital Expenditures In Five Years	$ 84.3
Climate Change [Abstract]
CO2 produced per year (in tons) | T	17
Remediation [Abstract]
Accrued environmental remediation expenses	$ 0.3	$ 0.3
Kansas City Power and Light Company [Member] | LaCygne Station [Member]
Best Available Retrofit Technology Rule [Abstract]
Predetermination request for environmental equipment required at LaCygne Station to comply with BART	$ 615
Entity's ownership percentage in facility (in hundredths)	50.00%
Cash capital expenditures for La Cygne environmental project	$ 524
KCPL Greater Missouri Operations [Member]
Remediation [Abstract]
Estimated amount of insurance proceeds available to cover qualified remediation expenses	$ 1.4
KCPL Greater Missouri Operations [Member] | Jeffrey Units Nos 1 and 2 [Member]
Best Available Retrofit Technology Rule [Abstract]
Entity's ownership percentage in facility (in hundredths)	8.00%
KCPL Greater Missouri Operations [Member] | Iatan No. 1 [Member]
Best Available Retrofit Technology Rule [Abstract]
Entity's ownership percentage in facility (in hundredths)	18.00%

Legal Proceedings Loss Continge

Legal Proceedings Loss Contingencies (Details) - Jun. 30, 2015 - USD ($) $ in Millions	Total
Loss Contingencies [Line Items]
Approximate amount of refunds received as a net purchaser of power through settlements with sellers of power	$ 8
Estimated additional refunds entitled to receive	$ 12
Unfavorable Regulatory Action [Member]
Loss Contingencies [Line Items]
Loss Contingency, Inestimable Loss	Due to the uncertainties remaining in the case, the potential refund or range of potential refunds owed by MPS Merchant are not reasonably estimable

Related Party Transactions an61

Related Party Transactions and Relationships (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Kansas City Power and Light Company [Member] | KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 33.8		$ 33.8		$ 38.2
KCPL employees manage GMO's business and operate its facilities at cost	46.2	$ 42.6	92.2	$ 87.2
KCPL net wholesale sales to GMO	0.1	$ 0.6	0.2	$ 11
Kansas City Power and Light Company [Member] | KCPL Greater Missouri Operations [Member] | Money Pool [Member]
Related Party Transaction [Line Items]
Payable to Related Party					12.6
Kansas City Power and Light Company [Member] | Great Plains Energy [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 20.3		$ 20.3		$ 18
Iatan No 1 And 2 [Member] | KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	18.00%		18.00%

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Futures contracts [Member] | Not Designated as Hedging Instrument [Member]
Price Risk Derivatives [Abstract]
Notional Contract Amount	$ 34.1	$ 14.9
Fair Value	(2.9)	(2.4)
Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Price Risk Derivatives [Abstract]
Notional Contract Amount	23.4	29.7
Fair Value	3.8	4.1
Option contracts [Member] | Not Designated as Hedging Instrument [Member]
Price Risk Derivatives [Abstract]
Notional Contract Amount	0	1.7
Fair Value	0	0.1
Transmission Congestion Rights [Member] | Not Designated as Hedging Instrument [Member]
Price Risk Derivatives [Abstract]
Notional Contract Amount	12.8	28.3
Fair Value	0.1	2.6
Kansas City Power and Light Company [Member] | Futures contracts [Member] | Not Designated as Hedging Instrument [Member]
Price Risk Derivatives [Abstract]
Notional Contract Amount	5.4	0
Fair Value	0	0
Kansas City Power and Light Company [Member] | Transmission Congestion Rights [Member] | Not Designated as Hedging Instrument [Member]
Price Risk Derivatives [Abstract]
Notional Contract Amount	9.5	23.6
Fair Value	$ 0.1	$ 3.1
KCPL Greater Missouri Operations [Member]
Price Risk Derivatives [Abstract]
Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged remainder of fiscal year	43.00%
Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged year two	29.00%
Percentage of expected on peak natural gas and natural gas equivalent purchased power price exposure hedged year three	10.00%

Derivative Instruments Cash Flo

Derivative Instruments Cash Flow Hedge (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015USD ($)
Derivative [Line Items]
Cash Flow Hedge Loss to be Reclassified within Twelve Months	$ 9.2
Kansas City Power and Light Company [Member]
Derivative [Line Items]
Cash Flow Hedge Loss to be Reclassified within Twelve Months	$ 8.8

Derivative Instruments Offsetti

Derivative Instruments Offsetting Assets (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 4.4	$ 8.6
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(0.5)	(1.2)
Derivative Asset	3.9	7.4
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	3.9	7.4
Kansas City Power and Light Company [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.5	4
Derivative Asset, Fair Value, Gross Liability and Obligation to Return Cash, Offset	(0.4)	(0.9)
Derivative Asset	0.1	3.1
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0.1	$ 3.1

Derivative Instruments Offset65

Derivative Instruments Offsetting Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 3.4	$ 4.2
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(3.3)	(3.5)
Derivative Liability	0.1	0.7
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0.1	0.7
Cash collateral posted with third parties as part of netting agreements	2.8	2.3
Kansas City Power and Light Company [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	0.4	0.9
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	(0.4)	(0.9)
Derivative Liability	0	0
Derivative, Collateral, Right to Reclaim Securities	0	0
Derivative, Collateral, Right to Reclaim Cash	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 0	$ 0

Derivative Instruments Fair Val

Derivative Instruments Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 4.4	$ 8.6
Derivative Liability, Fair Value, Gross Liability	3.4	4.2
Kansas City Power and Light Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.5	4
Derivative Liability, Fair Value, Gross Liability	0.4	0.9
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Other Balance Sheet Location [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	4.4	8.6
Derivative Liability, Fair Value, Gross Liability	3.4	4.2
Commodity Contract [Member] | Not Designated as Hedging Instrument [Member] | Other Balance Sheet Location [Member] | Kansas City Power and Light Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.5	4
Derivative Liability, Fair Value, Gross Liability	$ 0.4	$ 0.9

Derivative Instruments Gain and

Derivative Instruments Gain and Losses (Details) - Not Designated as Hedging Instrument [Member] - Commodity Contract [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement or regulatory account for changes in fair value of commodity contracts not designated as hedging	$ (1.1)	$ (7.5)	$ (13.2)	$ (4.8)
Regulatory Asset [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in regulatory account for changes in fair value of commodity contracts not designated as hedging	3.1	(4)	(3.2)	(4.1)
Regulatory Liability [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in regulatory account for changes in fair value of commodity contracts not designated as hedging	0	(0.9)	0	0.2
Kansas City Power and Light Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement or regulatory account for changes in fair value of commodity contracts not designated as hedging	(1.1)	(5.2)	(7.5)	(4.4)
Kansas City Power and Light Company [Member] | Regulatory Asset [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in regulatory account for changes in fair value of commodity contracts not designated as hedging	1.4	(2.1)	0	(2.2)
Purchased Power Costs [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement for changes in fair value of commodity contracts not designated as hedging	(1.1)	0	(1.2)	0.4
Fuel Costs [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement for changes in fair value of commodity contracts not designated as hedging	(0.6)	0.6	(1.1)	1
Fuel Costs [Member] | Kansas City Power and Light Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement for changes in fair value of commodity contracts not designated as hedging	0	0.1	0.2	0.1
Electric Revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement for changes in fair value of commodity contracts not designated as hedging	(2.5)	(3.2)	(7.7)	(2.3)
Electric Revenues [Member] | Kansas City Power and Light Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reflected in the income statement for changes in fair value of commodity contracts not designated as hedging	$ (2.5)	$ (3.2)	$ (7.7)	$ (2.3)

Fair Value Measurements Level 3

Fair Value Measurements Level 3 (Details) - Derivative Financial Instruments, Assets [Member] - Fair Value, Inputs, Level 3 [Member] - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net asset (liability) beginning of period	$ (1.2)	$ 6.9	$ 3.5	$ 3.3
Purchases	0.4	7.3	0.6	13.4
Settlements	1.6	(10.3)	1.9	(21.2)
Net asset (liability) end of period	0.8	0.6	0.8	0.6
Purchased Power Costs [Member]
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 Inputs Reconciliation, Gain (Loss) Included in Earnings	(1.1)	0	(1.2)	0.4
Non-Operating Income [Member]
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 Inputs Reconciliation, Gain (Loss) Included in Earnings	1.6	4	3.7	11.1
Total unrealized gains and (losses) relating to assets and liabilities still on the consolidated balance sheet at period end	0	0.1	(0.1)	0.2
Electric Revenues [Member]
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 Inputs Reconciliation, Gain (Loss) Included in Earnings	(2.5)	(3.2)	(7.7)	(2.3)
Total unrealized gains and (losses) relating to assets and liabilities still on the consolidated balance sheet at period end	0	(2.4)	0	(2.5)
Regulatory Asset [Member]
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 Inputs Reconciliation, Gain (Loss) Included in Regulatory Account	2	(4.1)	0	(4.1)
Total unrealized gains and (losses) relating to assets and liabilities still on the consolidated balance sheet at period end	0	(4.1)	0	(4.1)
Kansas City Power and Light Company [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net asset (liability) beginning of period	(0.8)	3.9	3.1	1.1
Purchases	0.2	6.7	(0.2)	11.8
Settlements	1.8	(4.4)	4.9	(7.5)
Net asset (liability) end of period	0.1	0.9	0.1	0.9
Kansas City Power and Light Company [Member] | Electric Revenues [Member]
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 Inputs Reconciliation, Gain (Loss) Included in Earnings	(2.5)	(3.2)	(7.7)	(2.3)
Total unrealized gains and (losses) relating to assets and liabilities still on the consolidated balance sheet at period end	0	(2.4)	0	(2.5)
Kansas City Power and Light Company [Member] | Regulatory Asset [Member]
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 Inputs Reconciliation, Gain (Loss) Included in Regulatory Account	1.4	(2.1)	0	(2.2)
Total unrealized gains and (losses) relating to assets and liabilities still on the consolidated balance sheet at period end	$ 0	$ (2.1)	$ 0	$ (2.2)

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Long-Term Debt (Details) - USD ($) $ in Billions	Jun. 30, 2015	Dec. 31, 2014
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair value of financial instruments [Abstract]
Long-term Debt	$ 3.5	$ 3.5
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Kansas City Power and Light Company [Member]
Fair value of financial instruments [Abstract]
Long-term Debt	2.3	2.3
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair value of financial instruments [Abstract]
Long-term debt fair value	3.8	3.8
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Kansas City Power and Light Company [Member]
Fair value of financial instruments [Abstract]
Long-term debt fair value	$ 2.5	$ 2.6

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Assets [Abstract]
Derivative instruments, assets		$ 4.4	$ 8.6
Liabilities [Abstract]
Derivative instruments, liabilities		3.4	4.2
Kansas City Power and Light Company [Member]
Assets [Abstract]
Derivative instruments, assets		0.5	4
Liabilities [Abstract]
Derivative instruments, liabilities		0.4	0.9
Fair Value, Measurements, Recurring [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	4.4	8.6
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value	[2]	203.3	199
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure	[3]	15.8	15.1
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure	[4]	17.4	17.9
Total assets		240.9	240.6
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	3.4	4.2
Total liabilities		3.4	4.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0.1	0
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value	[2]	167.9	162.3
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure	[3]	8.6	7.5
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure	[4]	0.1	0.1
Total assets		176.7	169.9
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	3	2.4
Total liabilities		3	2.4
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	3.1	3.4
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value	[2]	35.4	36.7
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure	[3]	7.2	7.6
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure	[4]	17.3	17.8
Total assets		63	65.5
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0	0.1
Total liabilities		0	0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	1.2	5.2
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value	[2]	0	0
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure	[3]	0	0
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure	[4]	0	0
Total assets		1.2	5.2
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0.4	1.7
Total liabilities		0.4	1.7
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0.5	4
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		203.3	199
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		15.8	15.1
SERP rabbi trust [Abstract]
Total assets		219.6	218.1
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0.4	0.9
Total liabilities		0.4	0.9
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Equity Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		140.1	137.1
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		1.2	1.3
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Debt Securities [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		7.2	7.6
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | US Treasury and Government [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		24.9	22.9
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | US Government Corporations and Agencies Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		2.1	3.5
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | US States and Political Subdivisions Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		4	4.1
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Corporate Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		28.8	28.1
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Foreign Government Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0.5	0.5
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Cash Equivalents [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		2.9	2.3
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Cash and Cash Equivalents [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		7.4	6.2
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Other Trust Assets [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value			0.5
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0.1	0
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		167.9	162.3
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		8.6	7.5
SERP rabbi trust [Abstract]
Total assets		176.6	169.8
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0.1	0
Total liabilities		0.1	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		140.1	137.1
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		1.2	1.3
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Securities [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury and Government [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		24.9	22.9
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Corporations and Agencies Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		2.9	2.3
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		7.4	6.2
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Other Trust Assets [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value			0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0	0
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		35.4	36.7
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		7.2	7.6
SERP rabbi trust [Abstract]
Total assets		42.6	44.3
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0	0
Total liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		7.2	7.6
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury and Government [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Corporations and Agencies Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		2.1	3.5
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		4	4.1
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		28.8	28.1
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0.5	0.5
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Cash Equivalents [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Other Trust Assets [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value			0.5
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0.4	4
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
SERP rabbi trust [Abstract]
Total assets		0.4	4
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0.3	0.9
Total liabilities		0.3	0.9
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Securities [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury and Government [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Corporations and Agencies Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government Debt Securities [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Cash Equivalents [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Self-insured health plan trust [Abstract]
Self Insured Health Plan Trust Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Kansas City Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Other Trust Assets [Member]
Nuclear decommissioning trust [Abstract]
Decommissioning Fund Investments, Fair Value			0
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	3.9	4.6
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		17.4	17.9
Total assets		21.3	22.5
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	3	3.3
Total liabilities		3	3.3
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Equity Securities [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0.1	0.1
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fixed Income Funds [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		17.3	17.8
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 1 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0	0
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0.1	0.1
Total assets		0.1	0.1
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	2.9	2.4
Total liabilities		2.9	2.4
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0.1	0.1
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed Income Funds [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 2 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	3.1	3.4
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		17.3	17.8
Total assets		20.4	21.2
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0	0.1
Total liabilities		0	0.1
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Income Funds [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		17.3	17.8
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 3 [Member]
Assets [Abstract]
Derivative instruments, assets	[1]	0.8	1.2
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0	0
Total assets		0.8	1.2
Liabilities [Abstract]
Derivative instruments, liabilities	[1]	0.1	0.8
Total liabilities		0.1	0.8
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring [Member] | Other Great Plains [Member] | Fair Value, Inputs, Level 3 [Member] | Fixed Income Funds [Member]
SERP rabbi trust [Abstract]
SERP Rabbi Trusts, Fair Value Disclosure		$ 0	$ 0
[1]	The fair value of derivative instruments is estimated using market quotes, over-the-counter forward price and volatility curves and correlations among fuel prices, net of estimated credit risk. Derivative instruments classified as Level 1 represent exchange traded derivative instruments. Derivative instruments classified as Level 2 represent non-exchange traded derivative instruments traded in over-the-counter markets. Derivative instruments classified as Level 3 represent non-exchange traded derivatives traded in over-the-counter markets for which observable market data is not available to corroborate the valuation inputs and TCRs valued at the most recent auction price in the SPP Integrated Marketplace.
[2]	Fair value is based on quoted market prices of the investments held by the fund and/or valuation models.
[3]	Fair value is based on quoted market prices of the investments held by the trust. Debt securities classified as Level 2 are comprised of corporate bonds, U.S. Agency, state and local obligations, and other asset-backed securities.
[4]	Fair value is based on quoted market prices for equity securities and Net Asset Value (NAV) per share for fixed income funds. The fixed income fund invests primarily in intermediate and long-term debt securities, can be redeemed immediately and is not subject to any restrictions on redemptions.

Accumulated Other Comprehensi71

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			$ (18.7)		$ (25.3)
Amounts reclassified from accumulated other comprehensive loss	[1]			3.1		5.5
Net current period other comprehensive income		$ 1.6	$ 2.5	3.1	[1]	5.5	[1]
Ending balance	[1]	(15.6)	(19.8)	(15.6)		(19.8)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			(15.8)		(23.8)
Amounts reclassified from accumulated other comprehensive loss	[1]			2.8		5.3
Net current period other comprehensive income	[1]			2.8		5.3
Ending balance	[1]	(13)	(18.5)	(13)		(18.5)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			(2.9)		(1.5)
Amounts reclassified from accumulated other comprehensive loss	[1]			0.3		0.2
Net current period other comprehensive income	[1]			0.3		0.2
Ending balance	[1]	(2.6)	(1.3)	(2.6)		(1.3)
Kansas City Power and Light Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance				(14.9)
Net current period other comprehensive income		1.3	1.4	2.7		2.7
Ending balance		(12.2)		(12.2)
Kansas City Power and Light Company [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]			(14.9)		(20.2)
Amounts reclassified from accumulated other comprehensive loss	[1]			2.7		2.7
Net current period other comprehensive income	[1]			2.7		2.7
Ending balance	[1]	$ (12.2)	$ (17.5)	$ (12.2)		$ (17.5)
[1]	Net of tax

Accumulated Other Comprehensi72

Accumulated Other Comprehensive Income (Loss) Reclassification (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest charges	$ (50)	$ (48.3)	$ (97.3)	$ (97.7)
Fuel	(99.9)	(115.4)	(207.5)	(250.6)
Utility operating and maintenance expenses	(183.4)	(183.4)	(354.9)	(364.1)
Income before income tax (expense) benefit and income (loss) from equity investments	68.5	79	93.6	110.8
Income tax (expense) benefit	(24.5)	(27)	(31)	(35.1)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(1.6)	(2.5)	(3.1)	(5.5)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income tax (expense) benefit and income (loss) from equity investments	(2.3)	(3.9)	(4.6)	(8.6)
Income tax (expense) benefit	0.9	1.4	1.8	3.3
Net income (loss)	(1.4)	(2.5)	(2.8)	(5.3)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest charges	(2.3)	(3.9)	(4.6)	(8.6)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Utility operating and maintenance expenses	(0.2)	(0.1)	(0.4)	(0.3)
Income before income tax (expense) benefit and income (loss) from equity investments	(0.2)	(0.1)	(0.4)	(0.3)
Income tax (expense) benefit	0	0.1	0.1	0.1
Net income (loss)	(0.2)	0	(0.3)	(0.2)
Kansas City Power and Light Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest charges	(34.1)	(31)	(65.6)	(61.7)
Fuel	(73.1)	(88.2)	(147.9)	(181.8)
Utility operating and maintenance expenses	(124.6)	(129.1)	(242.9)	(256.3)
Income before income tax (expense) benefit and income (loss) from equity investments	44.3	50.4	60.8	71.6
Income tax (expense) benefit	(14.9)	(15.6)	(18.2)	(19.6)
Kansas City Power and Light Company [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income tax (expense) benefit and income (loss) from equity investments	(2.1)	(2.2)	(4.4)	(4.4)
Income tax (expense) benefit	0.8	0.8	1.7	1.7
Net income (loss)	(1.3)	(1.4)	(2.7)	(2.7)
Kansas City Power and Light Company [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest charges	$ (2.1)	$ (2.2)	$ (4.4)	$ (4.4)

Income Tax Expense (Details)

Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Current income taxes
Federal	$ 0	$ (0.2)	$ 0.5	$ 0.1
State	0	0	(0.1)	0.1
Current Income Tax Expense (Benefit), Total	0	(0.2)	0.4	0.2
Deferred income taxes
Federal	20.3	25	25.4	31.6
State	4.5	5.1	5.9	6.8
Deferred Income Tax Expense (Benefit), Total	24.8	30.1	31.3	38.4
Noncurrent income taxes
Federal	0	(2.4)	0	(2.4)
State	0	(0.3)	0	(0.3)
Foreign	0	0.2	0	0
Noncurrent Income Tax Expense (Benefit), Total	0	(2.5)	0	(2.7)
Investment tax credit
Investment tax credit amortization	(0.3)	(0.4)	(0.7)	(0.8)
Total income tax expense	$ 24.5	$ 27	$ 31	$ 35.1
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	35.00%	35.00%	35.00%	35.00%
Differences between book and tax depreciation not normalized (in hundredths)	1.30%	(0.60%)	0.80%	(0.90%)
Amortization of investments tax credits (in hundredths)	(0.50%)	(0.50%)	(0.80%)	(0.70%)
Federal income tax credits (in hundredths)	(4.00%)	(3.80%)	(5.60%)	(5.40%)
State income taxes (in hundredths)	3.80%	3.80%	3.70%	3.80%
Changes in uncertain tax positions, net (in hundredths)	0.00%	0.30%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Other Adjustments	(0.10%)	(0.20%)	(0.30%)	(0.30%)
Effective Income Tax Rate Reconciliation, Percent	35.50%	34.00%	32.80%	31.50%
Kansas City Power and Light Company [Member]
Current income taxes
Federal	$ 4.2	$ (2)	$ (1.5)	$ 0.7
State	0.7	(0.3)	(0.4)	0.2
Current Income Tax Expense (Benefit), Total	4.9	(2.3)	(1.9)	0.9
Deferred income taxes
Federal	7.9	14.9	16.2	15.3
State	2.4	3.3	4.4	3.9
Deferred Income Tax Expense (Benefit), Total	10.3	18.2	20.6	19.2
Investment tax credit
Investment tax credit amortization	(0.3)	(0.3)	(0.5)	(0.5)
Total income tax expense	$ 14.9	$ 15.6	$ 18.2	$ 19.6
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory income tax (in hundredths)	35.00%	35.00%	35.00%	35.00%
Differences between book and tax depreciation not normalized (in hundredths)	2.00%	(0.90%)	1.30%	(1.80%)
Amortization of investments tax credits (in hundredths)	(0.60%)	(0.50%)	(0.90%)	(0.70%)
Federal income tax credits (in hundredths)	(6.20%)	(5.90%)	(8.70%)	(8.30%)
State income taxes (in hundredths)	4.10%	3.80%	4.00%	3.70%
Effective Income Tax Rate Reconciliation, Other Adjustments	(0.60%)	(0.50%)	(0.70%)	(0.60%)
Effective Income Tax Rate Reconciliation, Percent	33.70%	31.00%	30.00%	27.30%

Segments and Related Informat74

Segments and Related Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended			12 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Operating revenues		$ 609	$ 648.4	$ 1,158.1		$ 1,233.5
Depreciation and amortization		(83.5)	(75.6)	(163.3)		(150.1)
Interest charges		(50)	(48.3)	(97.3)		(97.7)
Income tax (expense) benefit		(24.5)	(27)	(31)		(35.1)
Net income (loss)		44.4	52.1	63.3		75.9
Assets, Total		10,762.2		10,762.2			$ 10,475.7
Capital expenditures				366.8	[1]	352.9	773.7	[1]
Operating Segments [Member] | Electric Utility Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues		609	648.4	1,158.1		1,233.5
Depreciation and amortization		(83.5)	(75.6)	(163.3)		(150.1)
Interest charges		(47.9)	(46)	(93.2)		(93)
Income tax (expense) benefit		(25.6)	(28)	(33.5)		(37.8)
Net income (loss)		46.4	54.7	67.3		80.8
Assets, Total		11,039.4		11,039.4			10,746.1
Capital expenditures	[1]			366.8			773.7
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0		0
Depreciation and amortization		0	0	0		0
Interest charges		(10.1)	(11.7)	(20.1)		(24.3)
Income tax (expense) benefit		1.1	1	2.5		2.7
Net income (loss)		(2)	(2.6)	(4)		(4.9)
Assets, Total		126.1		126.1			33.1
Capital expenditures	[1]			0			0
Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues		0	0	0		0
Depreciation and amortization		0	0	0		0
Interest charges		8	9.4	16		19.6
Income tax (expense) benefit		0	0	0		0
Net income (loss)		0	$ 0	0		$ 0
Assets, Total		$ (403.3)		(403.3)			(303.5)
Capital expenditures	[1]			$ 0			$ 0
[1]	Capital expenditures reflect year to date amounts for the periods presented.