Asset Impairment Expense (Details) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended
	Jan. 09, 2013 MW	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		$ 63,000,000	$ 0	$ 75,000,000	$ 48,000,000
Beaver Valley [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		0	0	0	46,000,000
Generation capacity mega watts	125
Lump sum payment received for termination of PPA	60,000,000
East Bend DPL [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		0	0	12,000,000	0
Generation capacity mega watts		186		186
Assets, fair value		2,000,000		2,000,000
Ebute [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		52,000,000	0	52,000,000	0
Assets, fair value		47,000,000		47,000,000
UK Wind (Newfield) [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		11,000,000	0	11,000,000	0
Assets, fair value		0		0
Other Impairment [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use		$ 0	$ 0	$ 0	$ 2,000,000