SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - VARIABLE INTEREST ENTITIES (Details) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)		Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) MW	Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)
Investments [Abstract]
Equity method investment	$ 2,517				$ 2,080					$ 2,517	$ 2,080
Assets [Abstract]
Cash and cash equivalents	288				349	[1]				288	349	[1]
Restricted cash	62				66	[1]				62	66	[1]
Inventories	307				258	[1]				307	258	[1]
Other	136				142	[1]				136	142	[1]
Total current assets	3,341				3,110	[1]				3,341	3,110	[1]
Sundry	792				520	[1]				792	520	[1]
Restricted cash	14				10	[1]				14	10	[1]
Property, plant and equipment, net	36,503				32,931	[1]				36,503	32,931	[1]
Total assets	50,454				47,786	[1]				50,454	47,786	[1]	$ 41,150
Liabilities [Abstract]
Current portion of long-term debt	1,427				913	[1]				1,427	913	[1]
Fixed-price contracts and other derivatives	109				83	[1]				109	83	[1]
Other	545				517	[1]				545	517	[1]
Total current liabilities	6,635				5,927	[1]				6,635	5,927	[1]
Asset retirement obligations	2,732				2,431	[1]				2,732	2,431	[1]
Deferred income taxes	2,767				3,745	[1]				2,767	3,745	[1]
Long-term debt	16,445				14,429	[1]				16,445	14,429	[1]
Fixed-price contracts and other derivatives	316				405	[1]				316	405	[1]
Equity [Abstract]
Other noncontrolling interests	2,450				2,270	[1]				2,450	2,270	[1]
Total liabilities and equity	50,454				47,786	[1]				50,454	47,786	[1]
Net assets less other noncontrolling interests	12,670				12,951	[1]				12,670	12,951	[1]
Operating Expenses [Abstract]
Energy-related businesses										1,431	922		977
Operation and maintenance										(3,117)	(2,970)		(2,886)
Depreciation and amortization										(1,490)	(1,312)	[2]	(1,250)	[2]
Income before income taxes										1,585	1,830		1,704
Other income, net										254	132		126
Interest expense										(659)	(553)		(561)
Income tax expense										(1,276)	(389)		(341)
Net income										351	1,519	[2]	1,448	[2]
(Earnings) losses attributable to noncontrolling interest										(94)	(148)		(98)
Earnings attributable to common shares	(501)	$ 57	$ 259	$ 441	379		$ 622	$ 16	$ 353	256	1,370		1,349
San Diego Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Gross long-term debt	4,573				4,349					4,573	4,349
Assets [Abstract]
Cash and cash equivalents	12				8	[1]				12	8	[1]
Restricted cash	6				11	[1]				6	11	[1]
Inventories	105				80	[1]				105	80	[1]
Other	4				3	[1]				4	3	[1]
Total current assets	1,100				1,072	[1]				1,100	1,072	[1]
Sundry	328				176	[1]				328	176	[1]
Restricted cash	11				1	[1]				11	1	[1]
Property, plant and equipment, net	14,838				13,250	[1]				14,838	13,250	[1]
Total assets	17,844				17,719	[1]				17,844	17,719	[1]
Liabilities [Abstract]
Current portion of long-term debt	220				191	[1]				220	191	[1]
Fixed-price contracts and other derivatives	60				61	[1]				60	61	[1]
Other	46				66	[1]				46	66	[1]
Total current liabilities	1,622				1,168	[1]				1,622	1,168	[1]
Asset retirement obligations	762				751	[1]				762	751	[1]
Deferred income taxes	1,530				2,829	[1]				1,530	2,829	[1]
Long-term debt	5,335				4,658	[1]				5,335	4,658	[1]
Fixed-price contracts and other derivatives	153				189	[1]				153	189	[1]
Equity [Abstract]
Other noncontrolling interests	28				37	[1]				28	37	[1]
Total liabilities and equity	17,844				17,719	[1]				17,844	17,719	[1]
Net assets less other noncontrolling interests	5,598				5,641	[1]				5,598	5,641	[1]
Operating Expenses [Abstract]
Income before income taxes										576	845		890
Operating income										713	990		1,058
Other income, net										66	50		36
Interest expense										(203)	(195)		(204)
Income tax expense										(155)	(280)		(284)
Net income										421	565	[2]	606	[2]
(Earnings) losses attributable to noncontrolling interest										$ (14)	5		(19)
San Diego Gas and Electric Company [Member] | Otay Mesa VIE [Member]
Variable Interest Entity [Line Items]
Generating capacity (in mw) | MW										605
Put option	280									$ 280
Investments [Abstract]
Equity of Variable interest entity	28				37					28	37
Assets [Abstract]
Cash and cash equivalents	4				6					4	6
Restricted cash	6				11					6	11
Inventories	4				3					4	3
Other	1				2					1	2
Total current assets	15				22					15	22
Restricted cash	11				1					11	1
Property, plant and equipment, net	321				354					321	354
Total assets	347				377					347	377
Liabilities [Abstract]
Current portion of long-term debt	10				10					10	10
Fixed-price contracts and other derivatives	10				13					10	13
Other	5				5					5	5
Total current liabilities	25				28					25	28
Long-term debt	284				293					284	293
Fixed-price contracts and other derivatives	3				12					3	12
Deferred credits and other	7				7					7	7
Equity [Abstract]
Other noncontrolling interests	28				37					28	37
Total liabilities and equity	347				377					347	377
Operating Expenses [Abstract]
Cost of electric fuel and purchased power										(79)	(79)		(83)
Operation and maintenance										(17)	(29)		(19)
Depreciation and amortization										(28)	(35)		(26)
Total operating expenses										(34)	(15)		(38)
Operating income										34	15		38
Other income, net										2	0		0
Interest expense										(22)	(20)		(19)
Net income										14	(5)		19
(Earnings) losses attributable to noncontrolling interest										(14)	5		(19)
Earnings attributable to common shares										0	0		$ 0
Sempra Renewables [Member]
Assets [Abstract]
Inventories	5				4					5	4
Sempra Renewables [Member] | Noncontrolling Tax Equity Investors [Member]
Assets [Abstract]
Cash and cash equivalents	23				88					23	88
Accounts receivable – trade, net	5				3					5	3
Inventories	1				0					1	0
Other	1				0					1	0
Total current assets	30				91					30	91
Sundry	2				0					2	0
Property, plant and equipment, net	1,412				926					1,412	926
Total assets	1,444				1,017					1,444	1,017
Liabilities [Abstract]
Accounts payable	42				68					42	68
Other	1				7					1	7
Total current liabilities	43				75					43	75
Asset retirement obligations	40				27					40	27
Deferred income taxes	10				0					10	0
Deferred credits and other	1				0					1	0
Total liabilities	94				102					94	102
Equity [Abstract]
Other noncontrolling interests	631				468					631	468
Net assets less other noncontrolling interests	719				447					719	447
Operating Expenses [Abstract]
Energy-related businesses										61	2
Operation and maintenance										(9)	(1)
Depreciation and amortization										(32)	0
Income before income taxes										20	1
Income tax expense										(4)	0
Net income										16	1
(Earnings) losses attributable to noncontrolling interest										(23)	(4)
Earnings attributable to common shares										39	5
Sempra LNG & Midstream [Member]
Assets [Abstract]
Inventories	34				82					34	82
Sempra LNG & Midstream [Member] | Cameron LNG Holdings [Member]
Investments [Abstract]
Equity method investment	997									997
Otay Mesa Energy Center Loan Payable Currently Through April 2019 [Member] | San Diego Gas and Electric Company [Member] | Otay Mesa VIE [Member]
Variable Interest Entity [Line Items]
Gross long-term debt	$ 295				$ 305					$ 295	$ 305

[1] Reflects reclassifications to conform to current year presentation, which we discuss in Note 1.

[2] As adjusted for the retrospective adoption of ASU 2016-15 and ASU 2016-18, which we discuss in Note 2.