Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified					12 Months Ended			0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended			12 Months Ended	0 Months Ended				1 Months Ended			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Mission Energy Holding Company	Dec. 31, 2011 American Bituminous Power Partners, L.P.	Dec. 31, 2011 Pinnacle Wind Force	Dec. 31, 2011 Broken Bow I, LLC	Feb. 13, 2012 Broken Bow I, LLC Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions MW	Dec. 31, 2011 Crofton Bluffs	Feb. 13, 2012 Crofton Bluffs Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions MW	Dec. 31, 2011 Laredo Ridge	Feb. 13, 2012 Cedro Hill Wind, LLC Sale of Ownership MW	Feb. 13, 2012 Mountain Wind Power Project Sale of Ownership MW	Feb. 13, 2012 Mountain Wind Power II Project Sale of Ownership MW	Dec. 31, 2011 Capistrano Wind Partners Mission Energy Holding Company	Feb. 13, 2012 Capistrano Wind Partners Sale of Ownership	Feb. 13, 2012 Capistrano Wind Partners Agreement to Sell Ownership, Upon Satisfaction of Specific Conditions	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary	Dec. 31, 2010 Variable Interest Entity, Primary Beneficiary	Apr. 30, 2011 Variable Interest Entity, Primary Beneficiary EMG Wind Projects	Dec. 31, 2011 Variable Interest Entity, Primary Beneficiary EMG Wind Projects MW projects	Dec. 31, 2010 Variable Interest Entity, Primary Beneficiary EMG Wind Projects MW projects	Dec. 31, 2011 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts projects contracts MW agreements	Dec. 31, 2010 Variable Interest Entity, Not Primary Beneficiary SCE Power Purchase Contracts
Details of projects or entities
Number of projects																					0	14	16
Number of Projects Consolidated																					13	14
Power generating capacity for majority interest (in megawatts)																					570	580	3,820
Sale of ownership interest (as a percent)																				75.00%
Summarized balance sheet information of VIEs
Current assets	$ 4,484	$ 4,422																$ 36	$ 26
Net property, plant and equipment	4,547	5,406																675	739
Other long-term assets	706	644																5	6
Total assets	48,039	45,530	41,444															716	771
Current liabilities	4,348	3,952																28	25
Long-term debt net of current portion	13,689	12,371																57	71
Deferred revenues																		69	71
Other long-term liabilities	2,476	2,041																22	21
Total liabilities	36,953	34,036																176	188
Noncontrolling interests	1,031	911																2	4
Assets serving as collateral for the debt obligations																		136	163
Ownership percentage					50.00%	100.00%	100.00%		100.00%		100.00%				100.00%
Sale of ownership, in megawatts								80		40		150	61	80
Outside investors contribution																238	141
Preferred investment made				4
Preferred equity interests to receive percent of cash available for distribution															100.00%
Cash available for distribution includes percent of tax benefits to be realized															90.00%
Power Purchase Agreement With Tolling Agreement																							6
Power Purchase Agreement With Qualified Facilities																							10
Payments to unconsolidated VIEs, power purchase contracts																							$ 477	$ 534