Investments in Unconsolidated Affiliates (Investments in Equity Method Unconsolidated Affiliates) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investments In Unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	$ 499	$ 358
Equity in earnings (losses) of unconsolidated affiliates	69	130	$ 122
Regulated Utilities [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	2	3
Equity in earnings (losses) of unconsolidated affiliates	(4)	(3)	(1)
International Energy [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	39	69
Equity in earnings (losses) of unconsolidated affiliates	74	120	110
Commercial Power [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	433	258
Equity in earnings (losses) of unconsolidated affiliates	(3)	10	7
Other [Member]
Investments In Unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	25	28
Equity in earnings (losses) of unconsolidated affiliates	$ 2	$ 3	$ 6