Derivative Instruments (Notional Values) (Details) - SCE - Electric Utility - Gross amounts recognized MWh in Thousands	Dec. 31, 2017 Bcfe MWh	Dec. 31, 2016 Bcfe MWh
Electricity options, swaps and forwards (GWh)
Derivatives
Notional volumes of derivative instruments	475	1,816
Natural gas options, swaps and forwards (Bcf)
Derivatives
Notional volumes of derivative instruments | Bcfe	143	36
Congestion revenue rights (GWh)
Derivatives
Notional volumes of derivative instruments	78,765	93,319
Tolling arrangements (GWh)
Derivatives
Notional volumes of derivative instruments	0	61,093