SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 712		$ 712		$ 658
Gross unrealized gains	332		332		372
Gross unrealized losses	(3)		(3)		(4)
Estimated fair value	1,041		1,041		1,026
Proceeds from sales	259	$ 282	1,082	$ 486
Gross realized gains	8	24	132	32
Gross realized losses	(3)	$ (3)	$ (11)	$ (14)
Period of significant cash withdrawals			10 years
Total debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	496		$ 496		396
Gross unrealized gains	11		11		6
Gross unrealized losses	(1)		(1)		(3)
Estimated fair value	506		506		399
U.S. government corporations and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	51		51		52
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Estimated fair value	51		51		52
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	238		238		203
Gross unrealized gains	7		7		4
Gross unrealized losses	0		0		(1)
Estimated fair value	245		245		206
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	207		207		141
Gross unrealized gains	4		4		2
Gross unrealized losses	(1)		(1)		(2)
Estimated fair value	210		210		141
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	189		189		143
Gross unrealized gains	321		321		366
Gross unrealized losses	(2)		(2)		(1)
Estimated fair value	508		508		508
Cash and cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	27		27		119
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Estimated fair value	$ 27		$ 27		$ 119