Quarterly Operating Results (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2012

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter
Great Plains Energy	1st			2nd		3rd		4th
2012	(millions, except per share amounts)
Operating revenue	$	479.7		$	603.6	$	746.2	$	480.4
Operating income	49.0			150.0		277.0		62.9
Net income (loss)	(9.3		)	58.1		146.4		4.7
Net income (loss) attributable to Great Plains Energy	(9.1		)	58.1		146.2		4.7
Basic and diluted earnings (loss) per common share	(0.07		)	0.41		0.95		0.03
2011
Operating revenue	$	492.9		$	565.1	$	773.7	$	486.3
Operating income	41.2			115.6		262.7		60.3
Net income	2.3			43.4		126.6		1.9
Net income attributable to Great Plains Energy	2.4			43.4		126.5		2.1
Basic earnings per common share	0.02			0.32		0.93		0.01
Diluted earnings per common share	0.01			0.31		0.91		0.01

	Quarter
KCP&L	1st		2nd		3rd		4th
2012	(millions)
Operating revenue	$	327.0	$	409.1	$	508.0	$	335.8
Operating income	31.6		99.9		177.8		39.4
Net income	2.3		43.7		90.2		5.4
2011
Operating revenue	$	330.8	$	383.4	$	506.3	$	337.8
Operating income	26.5		77.8		169.2		47.7
Net income	4.0		33.4		85.4		12.7