SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - OTHER INCOME, NET (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income [Line Items]
Allowance for equity funds used during construction	$ 168	$ 116	$ 107
Investment gains	56	23	3
Gains (losses) on interest rate and foreign exchange instruments, net	47	(32)	(4)
Foreign currency transaction losses(2)	(35)	(1)	(7)
Sale of other investments	3	5	11
Electrical infrastructure relocation income	3	10	7
Regulatory Interest, net	3	4	3
Sundry, net	9	7	6
Total	254	132	126
Foreign currency transaction losses	35	1	7
San Diego Gas and Electric Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	63	46	37
Regulatory Interest, net	3	3	3
Sundry, net	0	1	(4)
Total	66	50	36
Southern California Gas Company [Member]
Other Income [Line Items]
Allowance for equity funds used during construction	44	40	36
Regulatory Interest, net	0	1	0
Sundry, net	(8)	(9)	(6)
Total	36	$ 32	$ 30
Sempra Mexico [Member] | IMG [Member]
Other Income [Line Items]
Foreign currency transaction losses	$ 35