Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	$ 370	$ 338	$ 432
Tax positions taken during the current year, Increases	55	46	41
Tax positions taken during a prior year, Increases	274	6	0
Tax positions taken during a prior year, Decreases	(20)	(20)	(108)
Tax positions taken during a prior year, Decreases for settlements during the period	0	0	(27)
Balance at December 31,	679	370	338
SCE
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	282	249	331
Tax positions taken during the current year, Increases	56	47	42
Tax positions taken during a prior year, Increases	4	6	0
Tax positions taken during a prior year, Decreases	(22)	(20)	(121)
Tax positions taken during a prior year, Decreases for settlements during the period	0	0	(3)
Balance at December 31,	$ 320	$ 282	$ 249