SAN ONOFRE NUCLEAR GENERATING STATION - NUCLEAR DECOMMISSIONING TRUSTS (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Cost		$ 726		$ 726			$ 701
Gross unrealized gains		306		306			336
Gross unrealized losses		(10)		(10)			(4)
Estimated fair value		1,022		1,022			1,033
Proceeds from sales		277	$ 466	487	$ 823
Gross realized gains		25	79	29	124
Gross realized losses		(2)	$ (3)	(5)	$ (8)
Total debt securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		552		552			514
Gross unrealized gains		4		4			10
Gross unrealized losses		(7)		(7)			(3)
Estimated fair value		549		549			521
U.S. government corporations and agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		57		57			54
Gross unrealized gains		0		0			0
Gross unrealized losses		0		0			0
Estimated fair value		57		57			54
Municipal bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		262		262			245
Gross unrealized gains		3		3			7
Gross unrealized losses		(2)		(2)			(2)
Estimated fair value		263		263			250
Other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		233		233			215
Gross unrealized gains		1		1			3
Gross unrealized losses		(5)		(5)			(1)
Estimated fair value		229		229			217
Equity securities [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		160		160			171
Gross unrealized gains		302		302			326
Gross unrealized losses		(3)		(3)			(1)
Estimated fair value		459		459			496
Cash and cash equivalents [Member]
Debt Securities, Available-for-sale [Line Items]
Cost		14		14			16
Gross unrealized gains		0		0			0
Gross unrealized losses		0		0			0
Estimated fair value		$ 14		$ 14			$ 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