Compensation and Benefit Plans (Changes in Plan Assets and Benefits Obligations Recognized in OCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Postretirement Benefits Other Than Pensions
Pension and Other Postretirement Benefits
Unrecognized prior service cost (credit) to be amortized	$ (1)
Pension Plans
Pension and Other Postretirement Benefits
Net loss (gain)	0	$ 6	$ 7
Settlement charges	6	0	0
Amortization of net loss	(10)	(10)	(15)
Total recognized in other comprehensive loss	(16)	(4)	(8)
Total recognized in expense and other comprehensive loss	76	97	110
Unrecognized net loss to be amortized	8
Unrecognized prior service cost (credit) to be amortized	3
Amount of net loss expected to be reclassified from other comprehensive loss	8
SCE | Postretirement Benefits Other Than Pensions
Pension and Other Postretirement Benefits
Unrecognized prior service cost (credit) to be amortized	(1)
SCE | Pension Plans
Pension and Other Postretirement Benefits
Net loss (gain)	3	4	(9)
Settlement charges	0	0	0
Amortization of net loss	(6)	(6)	(9)
Total recognized in other comprehensive loss	(3)	(2)	(18)
Total recognized in expense and other comprehensive loss	72	$ 91	$ 93
Unrecognized net loss to be amortized	6
Unrecognized prior service cost (credit) to be amortized	3
Amount of net loss expected to be reclassified from other comprehensive loss	$ 6