Asset Impairment Expense (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	3 Months Ended		9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended			9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jan. 09, 2013 Beaver Valley [Member] MW	Sep. 30, 2014 Beaver Valley [Member]	Sep. 30, 2013 Beaver Valley [Member]	Sep. 30, 2014 Beaver Valley [Member]	Sep. 30, 2014 Itabo (San Lorenzo) [Member]	Sep. 30, 2013 Itabo (San Lorenzo) [Member] MW	Sep. 30, 2014 Itabo (San Lorenzo) [Member]	Sep. 30, 2013 Itabo (San Lorenzo) [Member] MW	Sep. 30, 2014 East Bend DPL [Member] MW	Mar. 31, 2014 East Bend DPL [Member]	Sep. 30, 2013 East Bend DPL [Member]	Sep. 30, 2014 East Bend DPL [Member] MW	Sep. 30, 2013 East Bend DPL [Member]	Sep. 30, 2014 Ebute [Member]	Jun. 30, 2014 Ebute [Member]	Sep. 30, 2014 Ebute [Member]	Sep. 30, 2013 Ebute [Member] MW	Sep. 30, 2014 UK Wind (Newfield) [Member]	Jun. 30, 2014 UK Wind (Newfield) [Member]	Sep. 30, 2014 UK Wind (Newfield) [Member]	Sep. 30, 2014 Other Impairment [Member]	Sep. 30, 2013 Other Impairment [Member]	Sep. 30, 2014 Other Impairment [Member]	Sep. 30, 2013 Other Impairment [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 15,000,000	$ 16,000,000	$ 90,000,000	$ 64,000,000	$ 46,000,000	$ 0	$ 0	$ 0	$ 0	$ 15,000,000	$ 0	$ 15,000,000	$ 0	$ 12,000,000	$ 0	$ 12,000,000	$ 0	$ 15,000,000	$ 52,000,000	$ 67,000,000		$ 0	$ 11,000,000	$ 11,000,000	$ 0	$ 1,000,000	$ 0	$ 3,000,000
Generation capacity mega watts					125					35		35	186			186					294
Lump sum payment received for termination of PPA					60,000,000
Assets, fair value										7,000,000		7,000,000		2,000,000				36,000,000	47,000,000	36,000,000			0
Assets Carrying Amount Disclosure Nonrecurring										$ 22,000,000		$ 22,000,000