Investments (Summary of Changes in Fair Value of the Nuclear Decommissioning Trusts) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Summary Of Changes In The Fair Value [Roll Forward]
Balance at beginning of period	$ 4,331
Balance at end of period	4,290
Southern California Edison
Summary Of Changes In The Fair Value [Roll Forward]
Balance at beginning of period	4,331	$ 4,799
Gross realized gains	17	27
Gross realized losses	(3)	(2)
Unrealized gains, net	59	44
Other-than-temporary impairments	(7)	(4)
Interest and dividends	29	28
Contributions	0	7
Income taxes	(18)	0
Decommissioning disbursements	(116)	0
Administrative expenses and other	(2)	(3)
Balance at end of period	$ 4,290	$ 4,896