SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Cost		$ 726		$ 726			$ 701
Gross unrealized gains		327		327			336
Gross unrealized losses		(11)		(11)			(4)
Estimated fair value		1,042		1,042			1,033
Proceeds from sales		216	$ 259	703	$ 1,082
Gross realized gains		3	8	32	132
Gross realized losses		(1)	$ (3)	(6)	$ (11)
Total debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		543		543			514
Gross unrealized gains		3		3			10
Gross unrealized losses		(7)		(7)			(3)
Estimated fair value		539		539			521
U.S. government corporations and agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		51		51			54
Gross unrealized gains		0		0			0
Gross unrealized losses		(1)		(1)			0
Estimated fair value		50		50			54
Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		259		259			245
Gross unrealized gains		2		2			7
Gross unrealized losses		(3)		(3)			(2)
Estimated fair value		258		258			250
Other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		233		233			215
Gross unrealized gains		1		1			3
Gross unrealized losses		(3)		(3)			(1)
Estimated fair value		231		231			217
Equity securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		166		166			171
Gross unrealized gains		324		324			326
Gross unrealized losses		(4)		(4)			(1)
Estimated fair value		486		486			496
Cash and cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		17		17			16
Gross unrealized gains		0		0			0
Gross unrealized losses		0		0			0
Estimated fair value		$ 17		$ 17			$ 16
San Diego Gas and Electric Company [Member]
Debt Securities, Available-for-sale [Line Items]
Percent of dismantlement work expense		20.00%		20.00%
Authorized recovery amount, nuclear decommissioning trust funding		$ 362		$ 362		$ 60
SONGS 1 Decommissioning [Member]
Debt Securities, Available-for-sale [Line Items]
Environmental exit costs, anticipated cost	$ 207
SONGS 1 Decommissioning [Member] | San Diego Gas and Electric Company [Member]
Debt Securities, Available-for-sale [Line Items]
Environmental exit costs, anticipated cost	41
Environmental Exit Costs, Anticipated Internal Costs	3
SONGS 2 and 3 Decommissioning [Member]
Debt Securities, Available-for-sale [Line Items]
Environmental exit costs, anticipated cost	3,200
SONGS 2 and 3 Decommissioning [Member] | San Diego Gas and Electric Company [Member]
Debt Securities, Available-for-sale [Line Items]
Environmental exit costs, anticipated cost	638
Environmental Exit Costs, Anticipated Internal Costs	$ 43