Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1, 2017	$ 471
Tax positions taken during the current year, Increases	39
Tax positions taken during a prior year, Increases	1
Tax positions taken during a prior year, Decreases	(5)
Tax positions taken during a prior year, Decreases for settlements during the period	(83)
Balance at September 30, 2017	423
Southern California Edison
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1, 2017	371
Tax positions taken during the current year, Increases	39
Tax positions taken during a prior year, Increases	1
Tax positions taken during a prior year, Decreases	(4)
Tax positions taken during a prior year, Decreases for settlements during the period	(78)
Balance at September 30, 2017	$ 329