Summary of Significant Accounting Policies (New Accounting Guidance) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings		$ 9,286		$ 9,286		$ 9,188
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit income - non-service cost components			$ (1)		$ 7
Southern California Edison
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings		9,878		9,878		$ 9,607
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit income - non-service cost components		$ 27	$ 9	$ 53	$ 18
ASU 2014-09 | Difference between revenue guidance in effect before and after topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 5
Retained earnings, before tax	7
ASU 2016-07
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	5
Retained earnings, before tax	$ 8