SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cost	$ 737		$ 731
Gross unrealized gains	281		290
Gross unrealized losses	(4)		(2)
Estimated fair value	1,014		1,019
Proceeds from sales	288	$ 552
Gross realized gains	21	92
Gross realized losses	(2)	$ (5)
Total debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	633		625
Gross unrealized gains	25		36
Gross unrealized losses	(2)		0
Estimated fair value	656		661
U.S. government corporations and agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	67		64
Gross unrealized gains	0		1
Gross unrealized losses	0		0
Estimated fair value	67		65
Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	310		308
Gross unrealized gains	15		18
Gross unrealized losses	(1)		0
Estimated fair value	324		326
Other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	256		253
Gross unrealized gains	10		17
Gross unrealized losses	(1)		0
Estimated fair value	265		270
Equity securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	111		112
Gross unrealized gains	255		254
Gross unrealized losses	(2)		(2)
Estimated fair value	364		364
Cash and cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	8		3
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Estimated fair value	8		3
Receivables (payables), net [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	(15)		(9)
Gross unrealized gains	1		0
Gross unrealized losses	0		0
Estimated fair value	$ (14)		$ (9)