Summary of Significant Accounting Policies (Property, Plant and Equipment) (Details) - SCE - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Depreciation	$ 1,800	$ 1,700	$ 1,700
Depreciation expense stated as a percent of average original cost of depreciable utility plant (as a percent)	3.60%	3.60%	3.70%
AFUDC equity capitalized during construction	$ 121	$ 101	$ 104
Interest and other income
Property, Plant and Equipment [Line Items]
AFUDC equity capitalized during construction	121	101	104
Interest expense
Property, Plant and Equipment [Line Items]
AFUDC debt capitalized during construction	$ 53	$ 63	$ 44
Generation plant
Property, Plant and Equipment [Line Items]
Weighted Average Useful Lives	36 years
Distribution plant
Property, Plant and Equipment [Line Items]
Weighted Average Useful Lives	48 years
Transmission plant
Property, Plant and Equipment [Line Items]
Weighted Average Useful Lives	54 years
General plant and other
Property, Plant and Equipment [Line Items]
Weighted Average Useful Lives	25 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	45 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	55 years
Maximum | Distribution plant
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	65 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