Consolidated Statements of Income and Comprehensive Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Operating Revenues
Electric revenues	$ 600.3	$ 603.6	$ 1,142.5		$ 1,083.3
Operating Expenses
Fuel	121.2	138.1	253.4		257.4
Purchased power	34.9	26.9	73.7		51.6
Transmission of electricity by others	12.9	8.8	24.3		16.1
Utility operating and maintenance expenses	166.4	164.1	321.6		327.2
Depreciation and amortization	72.6	67.9	142.8		135.3
General taxes	48.1	45.0	95.9		89.5
Other General and Administrative Expense	0.6	2.8	1.1		7.2
Costs and Expenses, Total	456.7	453.6	912.8		884.3
Operating Income (Loss)	143.6	150.0	229.7		199.0
Non-operating income	4.4	1.6	6.9		2.5
Non-operating expenses	(2.2)	(5.8)	(3.5)		(7.6)
Interest charges	(49.4)	(55.8)	(99.1)		(122.7)
Income before income tax (expense) benefit and income (loss) from equity investments	96.4	90.0	134.0		71.2
Income tax (expense) benefit	(32.7)	(31.8)	(44.2)		(22.3)
Income (loss) from equity investments, net of income taxes	(0.1)	(0.1)	(0.2)		(0.1)
Net income (loss)	63.6	58.1	89.6		48.8
Less: Net income (loss) attributable to noncontrolling interest	0	0	0		0.2
Net income (loss) attributable to Great Plains Energy	63.6	58.1	89.6		49.0
Preferred stock dividend requirements	0.4	0.4	0.8		0.8
Earnings (loss) available for common shareholders	63.2	57.7	88.8		48.2
Average number of common shares outstanding (in shares)	153.5	139.6	153.4		137.7
Average number of diluted common shares outstanding	153.8	142.0	153.7		140.6
Basic earnings (loss) per common share
Basic earnings per share	$ 0.41	$ 0.41	$ 0.58		$ 0.35
Diluted earnings (loss) per common share
Diluted earnings per share	$ 0.41	$ 0.41	$ 0.58		$ 0.34
Cash dividends per common share	$ 0.2175	$ 0.2125	$ 0.435		$ 0.425
Comprehensive Income
Net income (loss)	63.6	58.1	89.6		48.8
Other comprehensive income
Gain (loss) on derivative hedging instruments	0	0.1	0		(0.2)
Income tax benefit (expense)	0	0	0		0.1
Net gain (loss) on derivative hedging instruments	0	0.1	0		(0.1)
Reclassification to expenses, net of tax	2.9	3.1	6.1		6.2
Derivative hedging activity, net of tax	2.9	3.2	6.1		6.1
Amortization of net losses included in net periodic benefit costs	0.3	0.1	0.3		0.2
Income tax benefit (expense)	(0.1)	(0.1)	(0.1)		(0.1)
Net change in unrecognized pension expense	0.2	0	0.2		0.1
Total other comprehensive income (loss)	3.1	3.2	6.3	[1]	6.2
Comprehensive income (loss)	66.7	61.3	95.9		55.0
Less: comprehensive income (loss) attributable to noncontrolling interest	0	0	0		0.2
Comprehensive income (loss) attributable to Great Plains Energy	66.7	61.3	95.9		55.2
Kansas City Power and Light Company [Member]
Operating Revenues
Electric revenues	410.8	409.1	777.5		736.1
Operating Expenses
Fuel	86.0	98.7	180.5		183.3
Purchased power	18.6	6.6	37.7		13.6
Transmission of electricity by others	8.8	6.1	16.8		11.1
Utility operating and maintenance expenses	116.7	115.9	224.9		233.8
Depreciation and amortization	49.6	46.0	97.2		91.7
General taxes	37.7	35.9	74.7		71.1
Costs and Expenses, Total	317.4	309.2	631.8		604.6
Operating Income (Loss)	93.4	99.9	145.7		131.5
Non-operating income	3.8	0.8	5.5		1.3
Non-operating expenses	(1.2)	(2.7)	(1.6)		(3.4)
Interest charges	(31.5)	(31.3)	(63.5)		(63.7)
Income before income tax (expense) benefit and income (loss) from equity investments	64.5	66.7	86.1		65.7
Income tax (expense) benefit	(20.3)	(23.0)	(25.7)		(19.7)
Net income (loss)	44.2	43.7	60.4		46.0
Comprehensive Income
Net income (loss)	44.2	43.7	60.4		46.0
Other comprehensive income
Gain (loss) on derivative hedging instruments	0	0.1	0		(0.2)
Income tax benefit (expense)	0	0	0		0.1
Net gain (loss) on derivative hedging instruments	0	0.1	0		(0.1)
Reclassification to expenses, net of tax	1.3	1.3	2.8		2.7
Derivative hedging activity, net of tax	1.3	1.4	2.8		2.6
Total other comprehensive income (loss)	1.3	1.4	2.8		2.6
Comprehensive income (loss) attributable to Great Plains Energy	$ 45.5	$ 45.1	$ 63.2		$ 48.6

[1] (a) Net of tax