Derivative Instruments (Notional Values) (Details) - SCE	3 Months Ended	12 Months Ended
	Mar. 31, 2021 GWh Bcfe	Dec. 31, 2020 GWh Bcfe
Electricity options, swaps and forwards (GWh)
Derivatives
Notional volumes of derivative instruments	528	1,581
Natural gas options, swaps and forwards (Bcf)
Derivatives
Notional volumes of derivative instruments | Bcfe	29	34
Congestion revenue rights (GWh)
Derivatives
Notional volumes of derivative instruments	36,365	41,151