Nuclear Plant Decommissioning Trust (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2016
Nuclear decommissioning trust fund [Roll Forward]
Beginning balance January 1	$ 200.7	$ 199.0
Contributions	0.8	3.3
Earned income, net of fees	1.1	3.4
Net realized gains	0.0	0.7
Net unrealized gains (losses)	2.2	(5.7)
Ending balance	204.8	200.7
Kansas City Power and Light Company [Member]
Nuclear decommissioning trust fund [Roll Forward]
Beginning balance January 1	200.7	199.0
Contributions	0.8	3.3
Earned income, net of fees	1.1	3.4
Net realized gains	0.0	0.7
Net unrealized gains (losses)	2.2	(5.7)
Ending balance	$ 204.8	$ 200.7
Kansas City Power and Light Company [Member] | Wolf Creek [Member]
Jointly Owned Utility Plant Interests [Line Items]
Ownership percentage in Wolf Creek, a nuclear generating unit (in hundredths)	47.00%		47.00%