GENERAL INFORMATION AND OTHER FINANCIAL DATA - OTHER INCOME (EXPENSE), NET (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017		Dec. 31, 2017
Other Income [Line Items]
Allowance for equity funds used during construction	$ 29	$ 40		$ 56	$ 112
Investment gains	6	14		5	30
(Losses) gains on interest rate and foreign exchange instruments, net	(55)	31		7	94
Foreign currency transaction gains, net	(41)	7		(11)	17
Non-service component of net periodic benefit credit	7	17		39	22
Interest on regulatory balancing accounts, net	1	0		1	2
Sundry, net	(1)	(1)		2	5
Total	(54)	108	[1]	99	282	[1]
Foreign currency transaction gain				43			$ 35
Equity (losses) earnings	(4)	18	[1]	(24)	13	[1]
San Diego Gas and Electric Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	16	16		34	31
Non-service component of net periodic benefit credit	8	4		17	8
Interest on regulatory balancing accounts, net	2	0		2	2
Sundry, net	(1)	(1)		0	0
Total	25	19	[1]	53	41	[1]
Southern California Gas Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	13	11		22	22
Non-service component of net periodic benefit credit	3	15		28	18
Interest on regulatory balancing accounts, net	(1)	0		(1)	0
Sundry, net	(2)	(2)		(3)	(2)
Total	13	24	[1]	46	38	[1]
Sempra Mexico [Member] | IMG [Member]
Other Income [Line Items]
Foreign currency loss	$ 47			$ 8
Foreign currency transaction gain		$ 6			$ 6

[1] As adjusted for the retrospective adoption of ASU 2017-07, which we discuss in Note 2, and a reclassification to conform to current year presentation, which we discuss in Note 1.