Property, Plant and Equipment (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	$ 5,955,000,000		$ 7,271,000,000
Accumulated depreciation	(1,408,000,000)		(1,865,000,000)
Competitive power generation and other property - net	4,547,000,000		5,406,000,000
Capitalized software, estimated amortization expense 2012 through 2016	174,000,000
Building, plant and equipment
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	4,708,000,000		4,572,000,000
Emission Allowances
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	672,000,000		1,305,000,000
Expected lives, minimum	25
Expected lives, maximum	33.75
Leasehold improvements
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	4,000,000		177,000,000
Furniture and Equipment
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	130,000,000		97,000,000
Expected lives, minimum	3
Expected lives, maximum	10
Land (including easements)
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	64,000,000		84,000,000
Construction work in progress
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	377,000,000	[1]	1,036,000,000	[1]
Wind Projects
Property, plant and equipment:
Competitive power generation and other property, plant and equipment - gross	1,600,000,000
Accumulated depreciation	(203,000,000)
Construction work in progress related to new gas and wind projects under construction	357,000,000		888,000,000
Southern California Edison Company
Property, plant and equipment:
Capitalized software costs	1,400,000,000		1,100,000,000
Capitalized software, accumulated amortization	491,000,000		393,000,000
Capitalized software, amortization expense	156,000,000		129,000,000		88,000,000
Southern California Edison Company | Software [Member]
Property, plant and equipment:
Expected lives, minimum	5
Expected lives, maximum	15
Edison Mission Group Inc.
Property, plant and equipment:
Impairment charges	$ 1,700,000,000

[1] Construction work in progress consisted of $357 million and $888 million at December 31, 2011 and 2010, respectively, for new gas and wind projects under construction.