Regulatory Assets and Liabilities (Schedule of Regulatory Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Current regulatory assets	$ 860	$ 703
Long-term regulatory assets	5,022	4,914
Southern California Edison
Regulatory Assets [Line Items]
Current regulatory assets	860	703
Long-term regulatory assets	5,022	4,914
Total regulatory assets	5,882	5,617
Southern California Edison | Regulatory balancing accounts
Regulatory Assets [Line Items]
Current regulatory assets	642	484
Long-term regulatory assets	175	143
Southern California Edison | Power contracts and energy derivatives
Regulatory Assets [Line Items]
Current regulatory assets	203	203
Long-term regulatory assets	741	799
Southern California Edison | Other
Regulatory Assets [Line Items]
Current regulatory assets	15	16
Long-term regulatory assets	49	51
Southern California Edison | Deferred income taxes, net of liabilities
Regulatory Assets [Line Items]
Long-term regulatory assets	3,306	3,143
Southern California Edison | Pensions and other postretirement benefits
Regulatory Assets [Line Items]
Long-term regulatory assets	265	271
Southern California Edison | Unamortized investments, net of accumulated amortization
Regulatory Assets [Line Items]
Long-term regulatory assets	117	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	160	168
Southern California Edison | Environmental Remediation
Regulatory Assets [Line Items]
Long-term regulatory assets	$ 137	$ 144