Investments In Unconsolidated Affiliates (Equity In Earnings Of Equity Method Unconsolidated Affiliates) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	$ 148	$ 160	$ 116
U S Franchised Electric And Gas [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	(5)
Commercial Power [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	14	6	7
International Energy [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	134	145	102
Other Investment Companies [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	5	9	7
Domestic Equity Method Investments [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	12	13	12
Domestic Equity Method Investments [Member] | U S Franchised Electric And Gas [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	(5)
Domestic Equity Method Investments [Member] | Commercial Power [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	14	6	7
Domestic Equity Method Investments [Member] | Other Investment Companies [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	3	7	5
International Equity Method Investments [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	136	147	104
International Equity Method Investments [Member] | International Energy [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	134	145	102
International Equity Method Investments [Member] | Other Investment Companies [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Equity in earnings (losses) of unconsolidated affiliates	$ 2	$ 2	$ 2