Related Party Transactions and Relationships (Details) (Kansas City Power and Light Company [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
KCPL Greater Missouri Operations [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 32.7	$ 26.2
KCPL employees manage GMO's business and operate its facilities at cost	223.6	207.9	202.7
KCPL net wholesale sales to GMO	25.6	29.4	18.2
KCPL Greater Missouri Operations [Member] | Money Pool [Member]
Related Party Transaction [Line Items]
Payable to Related Party	0.2
Great Plains Energy [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	17.5	13.8
Great Plains Energy [Member] | Money Pool [Member]
Related Party Transaction [Line Items]
Payable to Related Party		$ 3.8