SAN ONOFRE NUCLEAR GENERATING STATION - 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	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 717		$ 717		$ 658
Gross unrealized gains	316		316		372
Gross unrealized losses	(4)		(4)		(4)
Estimated fair value	1,029		1,029		1,026
Proceeds from sales	466	$ 111	823	$ 204
Gross realized gains	79	5	124	8
Gross realized losses	(3)	$ (3)	$ (8)	$ (11)
Period of significant cash withdrawals			10 years
Total debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	510		$ 510		396
Gross unrealized gains	11		11		6
Gross unrealized losses	(2)		(2)		(3)
Estimated fair value	519		519		399
U.S. government corporations and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	57		57		52
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Estimated fair value	57		57		52
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	256		256		203
Gross unrealized gains	8		8		4
Gross unrealized losses	(1)		(1)		(1)
Estimated fair value	263		263		206
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	197		197		141
Gross unrealized gains	3		3		2
Gross unrealized losses	(1)		(1)		(2)
Estimated fair value	199		199		141
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	196		196		143
Gross unrealized gains	305		305		366
Gross unrealized losses	(2)		(2)		(1)
Estimated fair value	499		499		508
Cash and cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	11		11		119
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Estimated fair value	$ 11		$ 11		$ 119