Derivative Instruments (Notional Values) (Details) - Southern California Edison - Electric Utility - Economic Hedges GWh in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017 GWh Bcfe	Dec. 31, 2016 GWh Bcfe
Electricity options, swaps and forwards (GWh)
Derivative [Line Items]
Notional volumes of derivative instruments	874	1,816
Natural gas options, swaps and forwards (Bcf)
Derivative [Line Items]
Notional volumes of derivative instruments | Bcfe	137	36
Congestion revenue rights (GWh)
Derivative [Line Items]
Notional volumes of derivative instruments	74,849	93,319
Tolling arrangements (GWh)
Derivative [Line Items]
Notional volumes of derivative instruments	0	61,093