Other Investments (Textual) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Investments [Line Items]
Proceeds from sale of securities	$ 2,122,000,000	$ 2,773,000,000	$ 1,432,000,000
Sale of lease investment	108,000,000
Southern California Edison
Other Investments [Line Items]
Contributions received for decommissioning trusts	23,000,000
Period of reviewing contributions from decommissioning trusts (in years)	3 years
Proceeds from sale of securities	2,122,000,000	2,773,000,000	1,432,000,000
Unrealized holding gains, net of losses	1,600,000,000	1,300,000,000
Beaver Valley Nuclear Plant
Other Investments [Line Items]
Gain (loss) on sale of leases, before tax	65,000,000
Gain (loss) on sale of leases, after tax	31,000,000
American Airlines Lease
Other Investments [Line Items]
Lease impairment charge, before tax		26,000,000
Lease impairment charge, after tax		$ 16,000,000