Investments (Nuclear Decommissioning Trusts) (Details) - Southern California Edison - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Other Investments [Line Items]
Unrealized holding gains, net of losses	$ 1,500		$ 1,600
Other-than-temporary impairments	159		$ 143
Deferred income taxes related to unrealized gains	375
Nuclear decommissioning trusts	4,000
Gross realized gains	61	$ 99
Gross realized losses	(8)	(16)
Unrealized gains (losses), net of losses	$ (63)	$ 20