Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	$ 529	$ 576	$ 815
Tax positions taken during the current year, Increases	36	54	65
Tax positions taken during a prior year, Increases	2	66	1
Tax positions taken during a prior year, Decreases	(96)	(165)	(143)
Tax positions taken during a prior year, Decreases for settlements during the period	0	(2)	(162)
Balance at December 31,	471	529	576
SCE
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	353	441	532
Tax positions taken during the current year, Increases	36	48	57
Tax positions taken during a prior year, Increases	0	23	0
Tax positions taken during a prior year, Decreases	(18)	(159)	(93)
Tax positions taken during a prior year, Decreases for settlements during the period	0	0	(55)
Balance at December 31,	$ 371	$ 353	$ 441