Investments (Nuclear Decommissioning Trusts) (Details) - Southern California Edison - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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			159		$ 143
Deferred income taxes related to unrealized gains	370		370
Nuclear decommissioning trusts	3,900		3,900
Gross realized gains	26	$ 13	87	$ 112
Gross realized losses	(2)	0	(10)	(16)
Unrealized gains (losses), net of losses	$ (5)	$ 59	$ (68)	$ 79