Investments In Unconsolidated Affiliates (Investments In Equity Method Unconsolidated Affiliates) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	$ 483	$ 460
U.S. Franchised Electric And Gas [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	5	5
Commercial Power [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	219	188
International Energy [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	81	91
Other Investment Companies [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	178	176
Domestic Equity Method Investments [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	392	360
Domestic Equity Method Investments [Member] | U.S. Franchised Electric And Gas [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	5	5
Domestic Equity Method Investments [Member] | Commercial Power [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	219	188
Domestic Equity Method Investments [Member] | Other Investment Companies [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	168	167
International Equity Method Investments [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	91	100
International Equity Method Investments [Member] | International Energy [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	81	91
International Equity Method Investments [Member] | Other Investment Companies [Member]
Investments In Unconsolidated Affiliates And Related Party Transactions [Line Items]
Investments in unconsolidated affiliates	$ 10	$ 9