SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Securities, Available-for-sale [Line Items]
Cost	$ 731	$ 701
Gross unrealized gains	259	336
Gross unrealized losses	(16)	(4)
Estimated fair value	974	1,033
Proceeds from sales	890	1,314	$ 1,134
Gross realized gains	42	157	111
Gross realized losses	(10)	(14)	$ (29)
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	556	514
Gross unrealized gains	6	10
Gross unrealized losses	(6)	(3)
Estimated fair value	556	521
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	52	54
Gross unrealized gains	1	0
Gross unrealized losses	0	0
Estimated fair value	53	54
Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	266	245
Gross unrealized gains	4	7
Gross unrealized losses	(1)	(2)
Estimated fair value	269	250
Other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	238	215
Gross unrealized gains	1	3
Gross unrealized losses	(5)	(1)
Estimated fair value	234	217
Equity securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	168	171
Gross unrealized gains	253	326
Gross unrealized losses	(10)	(1)
Estimated fair value	411	496
Cash and cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	7	16
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	$ 7	$ 16