Fair Value Disclosures (Estimated Fair Values Of Debt And Equity Instruments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Fair Value Disclosures [Abstract]
Long-Term Debt, Carrying Amount	$ 3,868		$ 3,867
Long-term debt, Fair Value	4,569	[1]	4,577
Transition Bonds issued by ACE Funding, Carrying Amount	323		332
Transition Bonds issued by ACE Funding, Fair Value	370	[2]	380
Long-Term Project Funding, Carrying Amount			15
Long-term Project Funding, Fair Value	$ 15		$ 15

[1] The carrying amount for Long-term debt is $3,868 million as of March 31, 2012.

[2] The carrying amount for Transition Bonds issued by ACE Funding, including amounts due within one year, is $323 million as of March 31, 2012.