GENERAL INFORMATION AND OTHER FINANCIAL DATA - OTHER INCOME (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017
Other Income [Line Items]
Allowance for equity funds used during construction	$ 27	$ 72
Investment gains	(1)	16
Gains on interest rate and foreign exchange instruments, net	62	63
Foreign currency transaction gains, net	30	10
Non-service component of net periodic benefit credit	32	5
Interest on regulatory balancing accounts, net	0	2
Sundry, net	3	6
Total	153	174	[1]
Foreign currency transaction gain	4			$ 35
Equity losses	(20)	(5)	[1]
San Diego Gas and Electric Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	18	15
Non-service component of net periodic benefit credit	9	4
Interest on regulatory balancing accounts, net	0	2
Sundry, net	1	1
Total	28	22	[1]
Southern California Gas Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	9	11
Non-service component of net periodic benefit credit	25	3
Sundry, net	(1)	0
Total	33	$ 14	[1]
Sempra Mexico [Member] | IMG [Member]
Other Income [Line Items]
Foreign currency transaction gain	39
Equity losses	$ 39

[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.