SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Cost	$ 729,000,000	$ 731,000,000
Gross unrealized gains	360,000,000	259,000,000
Gross unrealized losses	(7,000,000)	(16,000,000)
Estimated fair value	1,082,000,000	974,000,000
Proceeds from sales	914,000,000	890,000,000	$ 1,314,000,000
Gross realized gains	24,000,000	42,000,000	157,000,000
Gross realized losses	(5,000,000)	(10,000,000)	$ (14,000,000)
Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	57,000,000	52,000,000
Gross unrealized gains	0	1,000,000
Gross unrealized losses	0	0
Estimated fair value	57,000,000	53,000,000
Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	270,000,000	266,000,000
Gross unrealized gains	12,000,000	4,000,000
Gross unrealized losses	0	(1,000,000)
Estimated fair value	282,000,000	269,000,000
Other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	218,000,000	238,000,000
Gross unrealized gains	9,000,000	1,000,000
Gross unrealized losses	(1,000,000)	(5,000,000)
Estimated fair value	226,000,000	234,000,000
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	545,000,000	556,000,000
Gross unrealized gains	21,000,000	6,000,000
Gross unrealized losses	(1,000,000)	(6,000,000)
Estimated fair value	565,000,000	556,000,000
Equity securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	176,000,000	168,000,000
Gross unrealized gains	339,000,000	253,000,000
Gross unrealized losses	(6,000,000)	(10,000,000)
Estimated fair value	509,000,000	411,000,000
Cash and cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Cost	8,000,000	7,000,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	$ 8,000,000	$ 7,000,000