Regulatory Assets and Liabilities (Schedule of Regulatory Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Current regulatory assets	$ 678	$ 703
Long-term regulatory assets	4,932	4,914
Southern California Edison
Regulatory Assets [Line Items]
Current regulatory assets	678	703
Long-term regulatory assets	4,932	4,914
Total regulatory assets	5,610	5,617
Southern California Edison | Regulatory balancing accounts
Regulatory Assets [Line Items]
Current regulatory assets	459	484
Long-term regulatory assets	160	143
Southern California Edison | Power contracts and energy derivatives
Regulatory Assets [Line Items]
Current regulatory assets	203	203
Long-term regulatory assets	774	799
Southern California Edison | Other
Regulatory Assets [Line Items]
Current regulatory assets	16	16
Long-term regulatory assets	36	51
Southern California Edison | Deferred income taxes, net of liabilities
Regulatory Assets [Line Items]
Long-term regulatory assets	3,202	3,143
Southern California Edison | Pensions and other postretirement benefits
Regulatory Assets [Line Items]
Long-term regulatory assets	268	271
Southern California Edison | Unamortized investments, net of accumulated amortization
Regulatory Assets [Line Items]
Long-term regulatory assets	116	123
Southern California Edison | San Onofre
Regulatory Assets [Line Items]
Long-term regulatory assets	72	72
Southern California Edison | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Long-term regulatory assets	164	168
Southern California Edison | Environmental remediation
Regulatory Assets [Line Items]
Long-term regulatory assets	$ 140	$ 144