Commitments and Contingencies (Other Lease Commitments) (Details) - SCE - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leased Assets [Line Items]
Operating leases expense	$ 59	$ 68	$ 80
Total
Operating Leased Assets [Line Items]
2018	48
2019	37
2020	27
2021	20
2022	15
Thereafter	99
Total future commitments	$ 246