Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1,	$ 432	$ 471
Tax positions taken during the current year, Increases	8	10
Tax positions taken during a prior year, Increases	0	2
Tax positions taken during a prior year, Decreases	(3)	(10)
Tax positions taken during a prior year, Decreases for settlements during the period	0	(82)
Balance at March 31,	437	391
Southern California Edison
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1,	331	371
Tax positions taken during the current year, Increases	8	10
Tax positions taken during a prior year, Increases	0	2
Tax positions taken during a prior year, Decreases	(3)	(10)
Tax positions taken during a prior year, Decreases for settlements during the period	0	(78)
Balance at March 31,	$ 336	$ 295