Acquisitions, Development and Divestitures (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 MW	Dec. 31, 2010
Development Projects [Abstract]
Number of plants anticipated to retire based on stricter EPA regulations or new construction	3
Combined capacity, in MW, of plants anticipated to retire based on stricter EPA regulations or new construction	797
Number of applicants that submitted loan guarantees to the DOE	10
Holtwood Hydroelectric Plant Expansion [Member]
Development Projects [Abstract]
Expected capital cost of an expansion project	$ 438,000,000
Capital cost unspent at the end of the period	196,000,000
Rainbow Hydroelectric Plant Expansion [Member]
Development Projects [Abstract]
Planned capacity (in MW) expansion	28
Expected capital cost of an expansion project	207,000,000
Capital cost unspent at the end of the period	29,000,000
Actual investments tax credits recorded	52,000,000	52,000,000
Forecasted investment tax credits	54,000,000
Susquehanna Nuclear Plant Expansion [Member]
Development Projects [Abstract]
Share of the total planned capacity (in MW) expansion when the company has a joint ownership interest	195
Completed capacity (in MW) expansion	50
Proposed Bell Bend Nuclear Unit [Member]
Development Projects [Abstract]
Number of applicants still active in DOE nuclear guarantee program	8
Current appropriated federal loan guarantees for nuclear projects	18,500,000,000
Maximum number of projects the DOE is expected to finance	3
Amount currently authorized by Board of Directors to spend on Bell Bend COLA	162,000,000
Capitalized costs associated with licensing efforts	131,000,000	109,000,000
Susquehanna Roseland Transmission Line [Member]
Development Projects [Abstract]
Expected capital cost of an expansion project	500,000,000
Total length (in miles) of the expansion project	150
Capacity (in kilovolts) of a transmission line	500
Total length (in miles) of the expansion project to be routed through Pennsylvania	100
Pending Bluegrass Plant Acquistion [Member]
Development Projects [Abstract]
Capacity of purchased units (in MW)	495
Purchase price	110,000,000
LG&E ownership percentage	69.00%
KU ownership percentage	31.00%
Proposed Natural Gas Fired Combined Cycle Turbine [Member]
Development Projects [Abstract]
Planned capacity (in MW) expansion	640
Expected capital cost of an expansion project	$ 580,000,000
Number of plants anticipated to retire based on stricter EPA regulations or new construction	6