Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Utility Plant, at Original Cost
Nuclear fuel, amortization	$ 188.0	$ 172.1
Shareholder's equity
Common stock - shares authorized (in shares)	600,000,000	600,000,000
Common stock-shares issued (in shares)	215,782,936	215,479,105
Treasury stock- shares (in shares)	135,166	128,087
Series B Preferred Stock [Member]
Shareholder's equity
Preferred Stock, Shares Issued	862,500	862,500
Preferred Stock, Dividend Rate, Percentage	7.00%	7.00%
Preferred Stock, Liquidation Preference Per Share	$ 1,000.00	$ 1,000.00
No Par Preference Stock [Member]
Shareholder's equity
Preference stock, Shares Authorized	11,000,000	11,000,000
Kansas City Power and Light Company [Member]
Utility Plant, at Original Cost
Nuclear fuel, amortization	$ 188.0	$ 172.1
Shareholder's equity
Common stock - shares authorized (in shares)	1,000.0	1,000.0
Common stock-shares issued (in shares)	1.0	1.0