Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Jan. 02, 2010
Net income	$ 174.2	$ 211.9	$ 150.4
Other comprehensive income (loss)
Gain (loss) on derivative hedging instruments	(5.9)	(28.0)	(0.4)
Income tax benefit (expense)	2.3	10.8	0.1
Net gain (loss) on derivative hedging instruments	(3.6)	(17.2)	(0.3)
Reclassification to expenses, net of tax (Note 18)	10.4	6.6	5.6
Derivative hedging activity, net of tax	6.8	(10.6)	5.3
Defined benefit pension plans
Net gain (loss) arising during period	(1.2)	(1.3)	5.0
Amortization of net gains included in net periodic benefit costs	0.4	0.3	0.4
Income tax benefit (expense)	0.3	0.4	(2.1)
Net change in unrecognized pension expense	(0.5)	(0.6)	3.3
Comprehensive income	180.5	200.7	159.0
Less: comprehensive income attributable to noncontrolling interest	0.2	(0.2)	(0.3)
Comprehensive income attributable to Great Plains Energy	180.7	200.5	158.7
Kansas City Power and Light Company [Member]
Net income	135.5	163.2	128.9
Other comprehensive income (loss)
Gain (loss) on derivative hedging instruments	(0.6)	(0.9)	0.2
Income tax benefit (expense)	0.2	0.3	(0.1)
Net gain (loss) on derivative hedging instruments	(0.4)	(0.6)	0.1
Reclassification to expenses, net of tax (Note 18)	5.4	5.7	5.3
Derivative hedging activity, net of tax	5.0	5.1	5.4
Defined benefit pension plans
Comprehensive income	$ 140.5	$ 168.3	$ 134.3