Other Investments (Amortized Cost and Fair Value of Nuclear Decommissioning Trusts) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Fair Value Disclosures:
Period of reviewing contributions from decommissioning trusts (in years)	3 years
Nuclear Decommissioning Trusts Disclosures
Amortized Cost	$ 2,381,000,000		$ 2,303,000,000
Fair Value	3,853,000,000	3,619,000,000	3,592,000,000	3,480,000,000
Proceeds from sale of securities	602,000,000	622,000,000
Unrealized holding gains, net of losses	1,500,000,000		1,300,000,000
Stocks
Nuclear Decommissioning Trusts Disclosures
Longest maturity dates decommissioning trust investments (in years)	0
Amortized Cost	885,000,000		865,000,000
Fair Value	2,124,000,000		1,899,000,000
Municipal bonds
Nuclear Decommissioning Trusts Disclosures
Longest maturity dates decommissioning trust investments (in years)	2051
Amortized Cost	574,000,000		625,000,000
Fair Value	696,000,000		756,000,000
U.S. government and agency securities
Nuclear Decommissioning Trusts Disclosures
Longest maturity dates decommissioning trust investments (in years)	2041
Amortized Cost	596,000,000		516,000,000
Fair Value	642,000,000		580,000,000
Corporate bonds
Nuclear Decommissioning Trusts Disclosures
Longest maturity dates decommissioning trust investments (in years)	2054
Amortized Cost	305,000,000		259,000,000
Fair Value	369,000,000		317,000,000
Short-term investments and receivables/payables
Nuclear Decommissioning Trusts Disclosures
Longest maturity dates decommissioning trust investments (in years)	One-year
Amortized Cost	21,000,000		38,000,000
Fair Value	22,000,000		40,000,000
Southern California Edison Company
Fair Value Disclosures:
Contributions received for decommissioning trusts	$ 23,000,000