Regulatory Assets and Liabilities (Schedule of Regulatory Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Regulatory Assets [Line Items]
Current regulatory assets	$ 913	$ 703
Long-term regulatory assets	5,046	4,914
Southern California Edison
Regulatory Assets [Line Items]
Current regulatory assets	913	703
Long-term regulatory assets	5,046	4,914
Total regulatory assets	5,959	5,617
Southern California Edison | Regulatory balancing accounts
Regulatory Assets [Line Items]
Current regulatory assets	694	484
Long-term regulatory assets	204	143
Southern California Edison | Power contracts and energy derivatives
Regulatory Assets [Line Items]
Current regulatory assets	205	203
Long-term regulatory assets	635	799
Southern California Edison | Other
Regulatory Assets [Line Items]
Current regulatory assets	14	16
Long-term regulatory assets	63	51
Southern California Edison | Deferred income taxes, net of liabilities
Regulatory Assets [Line Items]
Long-term regulatory assets	3,411	3,143
Southern California Edison | Pensions and other postretirement benefits
Regulatory Assets [Line Items]
Long-term regulatory assets	262	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	0	72
Southern California Edison | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Long-term regulatory assets	157	168
Southern California Edison | Environmental Remediation
Regulatory Assets [Line Items]
Long-term regulatory assets	135	144
Southern California Edison | Wildfire insurance costs
Regulatory Assets [Line Items]
Long-term regulatory assets	$ 63	$ 0