Nuclear Plant Decommissioning Trust (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Nuclear decommissioning trust fund [Roll Forward]
Nuclear decommissioning trust fund, beginning balance	$ 154,700,000	$ 135,300,000
Contributions to nuclear decommissioning trust fund	3,300,000	3,300,000
Nuclear decommissioning trust fund earned income, net of fees	2,700,000	3,000,000
Net realized gains (losses) on nuclear decommissioning trust fund	1,700,000	1,000,000
Net unrealized gains (losses) on nuclear decommissioning trust fund	21,500,000	12,100,000
Nuclear decommissioning trust fund, ending balance	183,900,000	154,700,000
Wolf Creek [Member]
Nuclear Plant Decommissioning Costs [Abstract]
Current cost of decommissioning (in 2011 dollars)	630,000,000
Future cost of decommissioning (in 2045 through 2053 dollars)	1,788,000,000
Annual Escalation Factor	2.85%
Annual return on trust assets through 2025	5.13%
Annual return on trusts assets beginning in 2053	0.76%
Nuclear Insurance [Abstract]
Industry aggregate limit on nuclear insurance for property claims including accidental damages	3,200,000,000
Industry aggregate limit on non-nuclear acts of terrorism	1,800,000,000
Amount of insurance against public liability claims resulting from nuclear incidents to full limit of public liability	13,600,000,000
Maximum available commercial insurance	400,000,000
Remaining balance provided through industry wide retrospective assesment program mandated by law	13,200,000,000
Maximum amount able to be assessed to owners	127,300,000
SFP Program-annual amount payable per incident	19,000,000
Amount of decontamination liability, premature decommissioning liability and property damage insurance	2,800,000,000
Premature decommissioning coverage applies only if property damage exceeds this amount and trust funds have been exhausted	500,000,000
Estimated maximum amount of retrospective assessments under the current policies	34,400,000
Ownership percentage in Wolf Creek, a nuclear generating unit (in hundredths)	47.00%
Kansas City Power and Light Company [Member]
Nuclear decommissioning trust fund [Roll Forward]
Nuclear decommissioning trust fund, beginning balance	154,700,000	135,300,000
Contributions to nuclear decommissioning trust fund	3,300,000	3,300,000
Nuclear decommissioning trust fund earned income, net of fees	2,700,000	3,000,000
Net realized gains (losses) on nuclear decommissioning trust fund	1,700,000	1,000,000
Net unrealized gains (losses) on nuclear decommissioning trust fund	21,500,000	12,100,000
Nuclear decommissioning trust fund, ending balance	183,900,000	154,700,000
Kansas City Power and Light Company [Member] | Wolf Creek [Member]
Nuclear Plant Decommissioning Costs [Abstract]
Current cost of decommissioning (in 2011 dollars)	296,000,000
Future cost of decommissioning (in 2045 through 2053 dollars)	840,000,000
Nuclear Insurance [Abstract]
Maximum amount able to be assessed to owners	59,800,000
SFP Program-annual amount payable per incident	8,900,000
Amount of decontamination liability, premature decommissioning liability and property damage insurance	1,300,000,000
Estimated maximum amount of retrospective assessments under the current policies	$ 16,100,000
Ownership percentage in Wolf Creek, a nuclear generating unit (in hundredths)	47.00%