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Summary of Significant Accounting Policies (Property, Plant and Equipment) (Details) - SCE - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Property, Plant and Equipment [Line Items]      
Depreciation $ 1,520 $ 1,420 $ 1,330
Depreciation expense stated as a percent of average original cost of depreciable utility plant (percent) 3.80% 3.90% 4.00%
Estimated cost of debt and equity funds for construction, capitalized $ 74 $ 87 $ 65
Interest and other income      
Property, Plant and Equipment [Line Items]      
Estimated cost of debt and equity funds for construction, capitalized 74 87 65
Interest expense      
Property, Plant and Equipment [Line Items]      
AFUDC debt capitalized during construction $ 23 $ 31 $ 25
Generation plant      
Property, Plant and Equipment [Line Items]      
Weighted-Average Useful Lives 38 years    
Distribution plant      
Property, Plant and Equipment [Line Items]      
Weighted-Average Useful Lives 43 years    
Transmission plant      
Property, Plant and Equipment [Line Items]      
Weighted-Average Useful Lives 53 years    
General plant and other      
Property, Plant and Equipment [Line Items]      
Weighted-Average Useful Lives 22 years    
Minimum | Generation plant      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 10 years    
Minimum | Distribution plant      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 20 years    
Minimum | Transmission plant      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 40 years    
Minimum | General plant and other      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 5 years    
Maximum | Generation plant      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 57 years    
Maximum | Distribution plant      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 60 years    
Maximum | Transmission plant      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 65 years    
Maximum | General plant and other      
Property, Plant and Equipment [Line Items]      
Estimated Useful Lives 60 years