Commitments and Contingencies (Schedule of Settlement Agreement) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Total pre-tax charge	$ 738	$ 21	$ 5
SCE
Loss Contingencies [Line Items]
Total pre-tax charge	716	$ 0	$ 0
Total after-tax charge	448
SCE | Utility Shareholder Agreement
Loss Contingencies [Line Items]
Total pre-tax charge	143
SCE | DOE litigation regulatory liability
Loss Contingencies [Line Items]
Total pre-tax charge	(72)
SCE | Arbitration with Mitsubishi Heavy Industries
Loss Contingencies [Line Items]
Total pre-tax charge	(47)
SCE | GHG Reduction Program
Loss Contingencies [Line Items]
Total pre-tax charge	(10)
SCE | San Onofre base regulatory asset
Loss Contingencies [Line Items]
Total pre-tax charge	696
SCE | Other
Loss Contingencies [Line Items]
Total pre-tax charge	$ 6