Variable Interest Entities (Details) (USD $)	9 Months Ended									9 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	1 Months Ended								3 Months Ended		9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011	Sep. 30, 2012 Mission Energy Holding Company	Feb. 13, 2012 Broken Bow I, LLC Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions MW	Feb. 13, 2012 Crofton Bluffs Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions MW	Feb. 13, 2012 Cedro Hill Wind, LLC MW	Feb. 13, 2012 Mountain Wind Power Project MW	Feb. 13, 2012 Mountain Wind Power II Project MW	Sep. 30, 2012 Capistrano Wind Partners	Feb. 13, 2012 Capistrano Wind Partners	Sep. 30, 2012 Capistrano Wind Partners Mission Energy Holding Company	Feb. 13, 2012 Capistrano Wind Partners Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions	Sep. 30, 2012 SCE Trust I	Sep. 30, 2012 SCE Trust I	May 31, 2012 SCE Trust I Trust Securities	Sep. 30, 2012 SCE Trust I Trust Securities	Sep. 30, 2012 SCE Trust I Series F	May 31, 2012 SCE Trust I Series F	Sep. 30, 2012 Variable Interest Entity, Primary Beneficiary	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary	Sep. 30, 2012 Variable Interest Entity, Primary Beneficiary EMG Wind Projects MW projects	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary EMG Wind Projects projects MW	Sep. 30, 2012 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts agreements MW contracts	Sep. 30, 2011 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts	Sep. 30, 2012 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts agreements MW contracts	Sep. 30, 2011 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts
Details of projects or entities
Number of projects (in projects)																								17		17
Number of projects consolidated (in projects)																						16	13
Power generating capacity for majority interest (in megawatts)																						861	570	3,900		3,900
Summarized balance sheet information of VIEs
Current assets	$ 4,494,000,000		$ 4,484,000,000																	$ 71,000,000	$ 36,000,000
Net property, plant and equipment	4,544,000,000		4,547,000,000																	1,090,000,000	675,000,000
Other long-term assets	725,000,000		684,000,000																	73,000,000	5,000,000
Total assets	50,545,000,000		48,039,000,000																	1,234,000,000	716,000,000
Current liabilities	4,274,000,000		4,348,000,000																	40,000,000	28,000,000
Long-term debt net of current portion	13,708,000,000		13,689,000,000																	172,000,000	57,000,000
Deferred revenues																				172,000,000	69,000,000
Long-term derivative liabilities	717,000,000		547,000,000																	23,000,000	0
Other long-term liabilities	2,887,000,000		2,475,000,000																	38,000,000	22,000,000
Total liabilities	38,525,000,000		36,953,000,000																	445,000,000	176,000,000
Noncontrolling interests	1,997,000,000		1,031,000,000																	238,000,000	2,000,000
Assets serving as collateral for the debt obligations																				467,000,000	136,000,000
Sale of ownership (in megawatts)					80	40	150	61	80
Outside investors contribution										238,000,000	238,000,000		140,000,000
Ownership percentage (as a percent)												100.00%
Preferred equity interests to receive percent of cash available for distribution (as a percent)										100.00%
Cash available for distribution includes percent of tax benefits to be realized (as a percent)										90.00%
Preferred investment made				4,000,000
Note receivable from sale of project companies				107,000,000
Tax effect upon transfer of assets to Capistrano Wind Partners	21,000,000	[1]
Power purchase agreement with tolling agreement (in agreements)																								7		7
Power purchase agreement with qualified facilities (in contracts)																								10		10
Payments to unconsolidated VIEs, power purchase contracts																								158,000,000	178,000,000	292,000,000	347,000,000
Unconsolidated Trust
Security dividend rate, (as a percent)																5.625%
Liquidation value (in dollars per share)																$ 25			$ 2,500
Liquidation preference																475,000,000
Common stock														10,000	10,000	0
Common stock, percentage issued to Southern California Edison																100.00%
Preference stock																	475,000,000	475,000,000	475,000,000
Dividend income and distributions														$ 7,000,000	$ 10,000,000

[1] Common stock was reduced by $21 million during the nine months ended September 30, 2012 due to a new tax basis in the assets transferred to Capistrano Wind Partners. For further information, see Note 3.