Summary of Significant Accounting Policies (Deferred Financing Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Regulatory assets	$ 4,914	$ 7,455
Edison International
Regulatory Assets [Line Items]
Amortization of deferred financing costs charged to interest expense	30	31	$ 33
Other long-term assets | Edison International
Regulatory Assets [Line Items]
Unamortized debt issuance expense	15	10
Long-term debt | Edison International
Regulatory Assets [Line Items]
Unamortized debt issuance expense	88	81
SCE
Regulatory Assets [Line Items]
Regulatory assets	4,914	7,455
Amortization of deferred financing costs charged to interest expense	27	27	$ 28
SCE | Other long-term assets
Regulatory Assets [Line Items]
Unamortized debt issuance expense	7	7
SCE | Long-term debt
Regulatory Assets [Line Items]
Unamortized debt issuance expense	77	71
SCE | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets	$ 168	$ 184