Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 months		Dec. 31, 2010		Dec. 31, 2009 segment
Summary of Significant Accounting Policies [Line Items]
Regulatory assets	$ 5,466,000,000		$ 4,347,000,000
Number of segments for financial reporting purposes	2				3
Cash Equivalents
Money market funds	1,300,000,000		1,100,000,000
Maximum maturity period of cash equivalent investments (in months)	3
Cash reclassified to accounts payable under cash management program	220,000,000		197,000,000
Restricted Cash and Deposits
Restricted cash related to lease payments, debt service, collateral reservers, or other	51,000,000		47,000,000
Inventory
Coal, gas, fuel oil and other raw materials	211,000,000		184,000,000
Spare parts, materials and supplies	413,000,000		384,000,000
Total inventory	624,000,000		568,000,000
Property, Plant and Equipment
AFUDC equity	96,000,000		100,000,000		116,000,000
Estimated useful lives and weighted-average useful lives of SCE's property, plant and equipment
Depreciation expense as a percentage of average original cost of depreciable utility plant (as a percent)	4.30%		4.10%		4.20%
Reconciliation of the changes in the ARO liability
Beginning balance	2,561,000,000		3,241,000,000
Accretion expense	68,000,000		198,000,000
Revisions	41,000,000	[1]	(867,000,000)	[1]
Liabilities added	19,000,000		9,000,000
Liabilities settled	(1,000,000)		(1,000,000)
Transfers in or out	0	[2]	(19,000,000)	[2]
Ending balance	2,688,000,000		2,561,000,000		3,241,000,000
Deferred Finance Costs
Unamortized debt issuance expense	134,000,000		114,000,000
Amortization of deferred financing costs	49,000,000		35,000,000		31,000,000
EMG Wind Projects
Income Taxes
Federal production tax credits carryforwards (in years)	10
Wind Financing
Restricted Cash and Deposits
Restricted deposits	97,000,000
Power Plant Facilities
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	3
Property, plant and equipment, useful lives, maximum (in years)	35
Emission Allowances
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	25
Property, plant and equipment, useful lives, maximum (in years)	33.75
Equipment, Furniture and Fixtures
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	3
Property, plant and equipment, useful lives, maximum (in years)	10
Capitalized Leased Equipment
Property, Plant and Equipment
Property, plant and equipment, useful lives, maximum (in years)	5
Other Current Assets
Property, Plant and Equipment
Purchased emission allowances	20,000,000		29,000,000
Other Long-Term Assets
Property, Plant and Equipment
Purchased emission allowances	92,000,000		31,000,000
Southern California Edison Company
Summary of Significant Accounting Policies [Line Items]
Regulatory assets	49,000,000
Property, Plant and Equipment
AFUDC equity	96,000,000		100,000,000		116,000,000
AFUDC debt	42,000,000		41,000,000		32,000,000
Revenue Recognition
Revenue received as a billing agent for long-term contracts with CDWR	1,100,000,000		1,200,000,000		1,800,000,000
Sales and Use Taxes
Franchise fees billed to customers	101,000,000		102,000,000		102,000,000
Dividend Restrictions
Minimum percentage of weighted-average common equity component authorization, set by CPUC (as a percent)	48.00%
Weighted-average common equity component authorization, set by CPUC remaining over number of months (in months)	13
Weighted-average common equity component of total capitalization (as a percent)	50.40%
Capacity to pay additional dividends	436,000,000
Related Party Transactions
Purchases from related parties	277,000,000		367,000,000		366,000,000
Southern California Edison Company | Generation Plant
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	25
Property, plant and equipment, useful lives, maximum (in years)	70
Estimated useful lives and weighted-average useful lives of SCE's property, plant and equipment
Weighted-average useful lives (in years)	40
Southern California Edison Company | Distribution Plant
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	30
Property, plant and equipment, useful lives, maximum (in years)	60
Estimated useful lives and weighted-average useful lives of SCE's property, plant and equipment
Weighted-average useful lives (in years)	40
Southern California Edison Company | Transmission Plant
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	35
Property, plant and equipment, useful lives, maximum (in years)	65
Estimated useful lives and weighted-average useful lives of SCE's property, plant and equipment
Weighted-average useful lives (in years)	46
Southern California Edison Company | General and Other Plant
Property, Plant and Equipment
Property, plant and equipment, useful lives, minimum (in years)	5
Property, plant and equipment, useful lives, maximum (in years)	60
Estimated useful lives and weighted-average useful lives of SCE's property, plant and equipment
Weighted-average useful lives (in years)	22
Edison Mission Group Inc.
Capitalized interest of major plant and facilities
Interest capitalized	27,000,000		54,000,000		19,000,000
Revenue Recognition
U.S. Treasury grants receivable	388,000,000
Revenue from power sales arrangements	109,000,000		81,000,000		83,000,000
Related Party Transactions
EMG ownership percentage, low end of the range (as a percent)	49.00%
EMG ownership percentage, high end of the range (as a percent)	50.00%
EMG ownership percentage in partnership, high end of the range (as a percent)	50.00%
Revenue from operation and maintenance agreements with related parties	23,000,000		23,000,000		26,000,000
Accounts receivable from affiliates	3,000,000		5,000,000
Electric Utility
Summary of Significant Accounting Policies [Line Items]
Supply of electricity, area covered (square mile)	50,000
San Onofre and Palo Verde | Southern California Edison Company
Reconciliation of the changes in the ARO liability
Ending balance	$ 2,500,000,000		$ 2,400,000,000

[1] Revisions in 2010 represent the most recent site-specific studies approved by the CPUC.

[2] Transfers in or out consist of the deconsolidation of the Big 4 projects (Kern River, Midway-Sunset, Sycamore and Watson) effective January 1, 2010. For further discussion, see Note 3.