Segments and Related Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]
Operating revenues	$ 585.1		$ 542.2
Depreciation and amortization	(74.5)		(70.2)
Interest charges	(49.4)		(49.7)
Income tax (expense) benefit	(8.1)		(11.5)
Net income (loss) attributable to Great Plains Energy	23.8		26.0
Assets, Total	9,884.9				9,795.4
Capital expenditures	185.2	[1]	172.2		669.0	[1]
Electric Utility Segment [Member] | Electric Utility Segment [Member]
Segment Reporting Information [Line Items]
Operating revenues	585.1		542.2
Depreciation and amortization	(74.5)		(70.2)
Interest charges	(47.0)		(47.8)
Income tax (expense) benefit	(9.8)		(12.6)
Net income (loss) attributable to Great Plains Energy	26.1		27.6
Assets, Total	10,150.9				10,019.6
Capital expenditures	185.2	[1]			669.0	[1]
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	0		0
Depreciation and amortization	0		0
Interest charges	(12.6)		(14.5)
Income tax (expense) benefit	1.7		1.1
Net income (loss) attributable to Great Plains Energy	(2.3)		(1.6)
Assets, Total	130.4				105.6
Capital expenditures	0	[1]	0	[1]
Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0		0
Depreciation and amortization	0		0
Interest charges	10.2		12.6
Income tax (expense) benefit	0		0
Net income (loss) attributable to Great Plains Energy	0		0
Assets, Total	(396.4)				(329.8)
Capital expenditures	$ 0	[1]	$ 0	[1]

[1] Capital expenditures reflect year to date amounts for the periods presented.