Consolidated Statements of Income and Comprehensive Income (unaudited) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Operating Revenues
Electric revenues	$ 746.2	$ 773.7	$ 1,829.5	$ 1,831.7
Operating Expenses
Fuel	164.7	146.5	422.1	365.8
Purchased power	17.9	68.1	69.5	178.4
Transmission of electricity by others	9.8	8.6	25.9	23.1
Utility operating and maintenance expenses	156.8	169.1	484.0	487.7
Voluntary separation program	0	0	0	12.7
Depreciation and amortization	68.9	65.9	204.2	205.9
General taxes	50.8	52.3	140.3	134.6
Other General and Administrative Expense	0.3	0.5	7.5	4.0
Costs and Expenses, Total	469.2	511.0	1,353.5	1,412.2
Operating income	277.0	262.7	476.0	419.5
Non-operating income	2.1	1.4	4.6	5.8
Non-operating expenses	(1.9)	(1.3)	(9.5)	(6.3)
Interest charges	(48.1)	(60.8)	(170.8)	(156.0)
Income from continuing operations before income tax	229.1	202.0	300.3	263.0
Income tax (expense) benefit	(82.6)	(75.4)	(104.9)	(90.6)
Loss from equity investments, net of income taxes	(0.1)	0	(0.2)	(0.1)
Net income	146.4	126.6	195.2	172.3
Less: Net income attributable to noncontrolling interest	(0.2)	(0.1)	0	0
Net income (loss) attributable to Great Plains Energy	146.2	126.5	195.2	172.3
Preferred stock dividend requirements	0.4	0.4	1.2	1.2
Earnings available for common shareholders	145.8	126.1	194.0	171.1
Average number of basic common shares outstanding	153.2	135.7	142.9	135.6
Average number of diluted common shares outstanding	153.4	138.3	145.0	138.5
Basic earnings (loss) per common share
Basic earnings per common share	$ 0.95	$ 0.93	$ 1.36	$ 1.26
Diluted earnings (loss) per common share
Diluted earnings per common share	$ 0.95	$ 0.91	$ 1.34	$ 1.24
Cash dividends per common share	$ 0.2125	$ 0.2075	$ 0.6375	$ 0.6225
Comprehensive Income
Net income	146.4	126.6	195.2	172.3
Derivative Hedging Activity
Gain (loss) on derivative hedging instruments	0.1	(0.1)	(0.1)	(5.5)
Income tax benefit (expense)	(0.1)	0.1	0	2.2
Net gain (loss) on derivative hedging instruments	0	0	(0.1)	(3.3)
Reclassification to expenses, net of tax	3.4	3.1	9.6	7.3
Derivative hedging activity, net of tax	3.4	3.1	9.5	4.0
Defined benefit pension plans
Amortization of net losses included in net periodic benefit costs	0.1	0	0.3	0.2
Income tax benefit (expense)	0	0	(0.1)	(0.1)
Net change in unrecognized pension expense	0.1	0	0.2	0.1
Other comprehensive income (loss)	3.5	3.1	9.7	4.1
Comprehensive income	149.9	129.7	204.9	176.4
Less: comprehensive income attributable to noncontrolling interest	(0.2)	(0.1)	0	0
Comprehensive income attributable to Great Plains Energy	149.7	129.6	204.9	176.4
Kansas City Power and Light Company [Member]
Operating Revenues
Electric revenues	508.0	506.3	1,244.1	1,220.5
Operating Expenses
Fuel	114.5	99.3	297.8	249.0
Purchased power	10.1	24.9	23.7	66.7
Transmission of electricity by others	6.3	5.7	17.4	14.2
Utility operating and maintenance expenses	110.5	120.2	344.3	350.7
Voluntary separation program	0	0	0	9.2
Depreciation and amortization	46.9	45.4	138.6	147.0
General taxes	41.9	41.6	113.0	108.9
Other General and Administrative Expense	0	0	0	1.3
Costs and Expenses, Total	330.2	337.1	934.8	947.0
Operating income	177.8	169.2	309.3	273.5
Non-operating income	1.0	0.8	2.3	1.8
Non-operating expenses	(1.3)	(1.0)	(4.7)	(3.4)
Interest charges	(32.4)	(30.8)	(96.1)	(81.2)
Income from continuing operations before income tax	145.1	138.2	210.8	190.7
Income tax (expense) benefit	(54.9)	(52.8)	(74.6)	(67.9)
Net income	90.2	85.4	136.2	122.8
Comprehensive Income
Net income	90.2	85.4	136.2	122.8
Derivative Hedging Activity
Gain (loss) on derivative hedging instruments	0.1	(0.1)	(0.1)	(0.2)
Income tax benefit (expense)	(0.1)	0.1	0	0.1
Net gain (loss) on derivative hedging instruments	0	0	(0.1)	(0.1)
Reclassification to expenses, net of tax	1.7	1.3	4.4	4.0
Derivative hedging activity, net of tax	1.7	1.3	4.3	3.9
Defined benefit pension plans
Other comprehensive income (loss)	1.7	1.3	4.3	3.9
Comprehensive income	$ 91.9	$ 86.7	$ 140.5	$ 126.7