Debt - Non-Recourse Debt Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Debt Instrument [Line Items]
Loss on extinguishment of debt	$ (23,000,000)	$ (134,000,000)
Nonrecourse Debt [Member] | Gener Subsidiary [Member]
Debt Instrument [Line Items]
Issued new debt	297,000,000
Nonrecourse Debt [Member] | Sul Subsidiary [Member]
Debt Instrument [Line Items]
Issued new debt	177,000,000
Repayments of Debt	$ 145,000,000