Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				0 Months Ended						3 Months Ended	0 Months Ended	3 Months Ended					3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011	Mar. 31, 2012 Mission Energy Holding Company	Feb. 13, 2012 Broken Bow I, LLC MW	Feb. 13, 2012 Crofton Bluffs 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	Feb. 13, 2012 Capistrano Wind Partners	Mar. 31, 2012 Capistrano Wind Partners Mission Energy Holding Company	Feb. 13, 2012 Capistrano Wind Partners Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions	Mar. 31, 2012 Cedro Hill, Mountain Wind Power I, and Mountain Wind Power II Projects [Member]	Mar. 31, 2012 Variable Interest Entity, Primary Beneficiary	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary	Mar. 31, 2012 Variable Interest Entity, Primary Beneficiary EMG Wind Projects MW projects	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary EMG Wind Projects projects MW	Mar. 31, 2012 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts agreements MW contracts	Mar. 31, 2011 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts
Details of projects or entities
Number of projects (in projects)																		16
Number of projects consolidated (in projects)																16	13
Power generating capacity for majority interest (in megawatts)																861	570	3,820
Summarized balance sheet information of VIEs
Current assets	$ 4,715		$ 4,484											$ 87	$ 36
Net property, plant and equipment	4,547		4,547											1,194	675
Other long-term assets	705		706											18	5
Total assets	49,384		48,039											1,299	716
Current liabilities	3,675		4,348											32	28
Long-term debt net of current portion	14,131		13,689											179	57
Deferred revenues														174	69
Other long-term liabilities	2,538		2,476											56	22
Total liabilities	37,777		36,953											441	176
Noncontrolling interests	1,617		1,031											246	2
Assets serving as collateral for the debt obligations														474	136
Sale of ownership (n megawatts)					80	40	150	61	80
Outside investors contribution										238		140
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
Tax effect upon transfer of assets to Capistrano Wind Partners	50	[1]
Income from projects attributable to noncontrolling interests													2
Power purchase agreement with tolling agreement (in agreements)																		6
Power purchase agreement with qualified facilities (in contracts)																		10
Payments to unconsolidated VIEs, power purchase contracts																		$ 78	$ 86

[1] Additional paid in capital was reduced $50 million related to a new tax basis in the assets transferred to Capistrano Wind Partners. For further information, see Note 3.The follow