Investments (Nuclear Decommissioning Trusts) (Details) - Southern California Edison - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Other Investments [Line Items]
Unrealized holding gains, net of losses	$ 1,500		$ 1,500		$ 1,600
Other-than-temporary impairments			151		$ 143
Deferred income taxes related to unrealized gains	382		382
Nuclear decommissioning trusts	3,900		3,900
Gross realized gains	28	$ 22	115	$ 134
Gross realized losses	(7)	(3)	(17)	(19)
Unrealized gains (losses), net of losses	$ 72	$ 62	$ 4	$ 141