Commitments and Contingencies (Energy Purchases, Other Commitments, Legal Matters and Regulatory Issues) (Details) (USD $)	3 Months Ended	1 Months Ended
	Mar. 31, 2015 mi Integer	Apr. 20, 2015 Integer
Legal Matters - Sierra Club Litigation (Numeric) [Abstract]
Number of separate claims included in the complaint against PPL Montana	39
Average requested amount, per day per violation, of injuctive relief and civil penalities	$ 36,000
Amount of civil penalities to be used for beneficial mitigation projects	100,000
Estimated number of post-2000 projects alleged not to be in compliance with the Clean Air Act	40
Number of plant projects that had claims dismissed under alleged Clean Air Act violations	3
Number of plant projects included in a second amended complaint under alleged Clean Air Act violations	8
Legal Matters - Cane Run Environmental Claims (Numeric) [Abstract]
Number of residents that filed class action suit	6
Number of miles within plant that would include a class of residents	4
Number of remaining unresolved Clean Air Act violation claims after July 2014 court ruling	1
Regulatory Issues - Maryland Capacity Order (Numeric) [Abstract]
Number electric utilities ordered to enter into long term contracts	3
Regulatory Issues - Pacific Northwest Markets (Numeric) [Abstract]
Amount for claims remaining unsettled at period end	50,000,000
Settlement amount reached with one of the parties	75,000
Amount of claim sought by City of Tacoma	23,000,000
Regulatory Issues - Electric - Reliability Standards (Numeric) [Abstract]
Maximum per day penalties for reliability violations	$ 1,000,000
Subsequent Event [Member]
Legal Matters - Sierra Club Litigation (Numeric) [Abstract]
Number of plant projects with remaining claims to be pursued by plaintiffs		4
LGE [Member]
Legal Matters - Cane Run Environmental Claims (Numeric) [Abstract]
Generating units retired at the Cane Run plant	1
Generating units anticipated to be retired at the Cane Run plant in the third quarter of 2015	2
PPL Electric Utilities Corp [Member]
Regulatory Issues - Maryland Capacity Order (Numeric) [Abstract]
Number electric utilities ordered to enter into long term contracts	3
LG And E And KU Energy LLC [Member]
Legal Matters - Cane Run Environmental Claims (Numeric) [Abstract]
Number of residents that filed class action suit	6
Number of miles within plant that would include a class of residents	4
Number of remaining unresolved Clean Air Act violation claims after July 2014 court ruling	1
LG And E And KU Energy LLC [Member] | LGE [Member]
Legal Matters - Cane Run Environmental Claims (Numeric) [Abstract]
Generating units retired at the Cane Run plant	1
Generating units anticipated to be retired at the Cane Run plant in the third quarter of 2015	2
Louisville Gas And Electric Co [Member]
Legal Matters - Cane Run Environmental Claims (Numeric) [Abstract]
Number of residents that filed class action suit	6
Number of miles within plant that would include a class of residents	4
Number of remaining unresolved Clean Air Act violation claims after July 2014 court ruling	1
Generating units retired at the Cane Run plant	1
Generating units anticipated to be retired at the Cane Run plant in the third quarter of 2015	2