SAN ONOFRE NUCLEAR GENERATING STATION (SONGS) - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 628		$ 628		$ 660
Gross unrealized gains	447		447		423
Gross unrealized losses	(7)		(7)		(20)
Estimated fair value	1,068		1,068		1,063
Proceeds from sales	282	$ 210	486	$ 431
Gross realized gains	24	18	32	24
Gross realized losses	(3)	$ (6)	(14)	$ (13)
Total debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	428		428		431
Gross unrealized gains	25		25		11
Gross unrealized losses	(4)		(4)		(13)
Estimated fair value	449		449		429
U.S. government corporations and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	95		95		89
Gross unrealized gains	5		5		2
Gross unrealized losses	0		0		0
Estimated fair value	100		100		91
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	150		150		148
Gross unrealized gains	11		11		8
Gross unrealized losses	0		0		0
Estimated fair value	161		161		156
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	183		183		194
Gross unrealized gains	9		9		1
Gross unrealized losses	(4)		(4)		(13)
Estimated fair value	188		188		182
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	188		188		214
Gross unrealized gains	422		422		412
Gross unrealized losses	(3)		(3)		(7)
Estimated fair value	607		607		619
Cash and cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	12		12		15
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Estimated fair value	$ 12		$ 12		$ 15