SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cost	$ 784		$ 784		$ 729
Gross unrealized gains	287		287		360
Gross unrealized losses	(14)		(14)		(7)
Estimated fair value	1,057		1,057		1,082
Proceeds from sales	294	$ 231	1,091	$ 728
Gross realized gains	9	5	108	18
Gross realized losses	(2)	$ (1)	(13)	$ (4)
Total debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	624		624		545
Gross unrealized gains	33		33		21
Gross unrealized losses	(2)		(2)		(1)
Estimated fair value	655		655		565
U.S. government corporations and agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	48		48		57
Gross unrealized gains	1		1		0
Gross unrealized losses	0		0		0
Estimated fair value	49		49		57
Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	318		318		270
Gross unrealized gains	18		18		12
Gross unrealized losses	(1)		(1)		0
Estimated fair value	335		335		282
Other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	258		258		218
Gross unrealized gains	14		14		9
Gross unrealized losses	(1)		(1)		(1)
Estimated fair value	271		271		226
Equity securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	147		147		176
Gross unrealized gains	254		254		339
Gross unrealized losses	(12)		(12)		(6)
Estimated fair value	389		389		509
Cash and cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	13		13		8
Gross unrealized gains	0		0		0
Gross unrealized losses	0		0		0
Estimated fair value	$ 13		$ 13		$ 8