Investments (Summary of Changes in Fair Value of the Nuclear Decommissioning Trusts) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Summary Of Changes In The Fair Value [Roll Forward]
Balance at beginning of period			$ 4,242
Balance at end of period	$ 4,381		4,381
Southern California Edison
Summary Of Changes In The Fair Value [Roll Forward]
Balance at beginning of period	4,352	$ 4,290	4,242	$ 4,331
Gross realized gains	13	22	112	75
Gross realized losses	0	(1)	(16)	(4)
Unrealized gains, net of losses	87	72	114	113
Other-than-temporary impairments	(3)	(8)	(4)	(33)
Interest and dividends	31	32	59	60
Income taxes	(26)	(24)	(26)	(42)
Decommissioning disbursements	(73)	(38)	(99)	(154)
Administrative expenses and other	0	(1)	(1)	(2)
Balance at end of period	$ 4,381	$ 4,344	$ 4,381	$ 4,344