SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - RECLASSIFICATION FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									$ (659)	$ (553)	$ (561)
Gain on sale of assets									3	134	70
Equity earnings, before income tax									34	6	104
Remeasurement of equity method investment									0	617	0
Equity earnings, net of income tax									42	78	85
Other income, net									254	132	126
Energy-related businesses									1,431	922	977
Income before income taxes									1,585	1,830	1,704
Income tax (expense) benefit									(1,276)	(389)	(341)
(Earnings) losses attributable to noncontrolling interest									(94)	(148)	(98)
Net income/Earnings	$ (501)	$ 57	$ 259	$ 441	$ 379	$ 622	$ 16	$ 353	256	1,370	1,349
Reclassification from AOCI, Net of taxes									19	18	18
San Diego Gas and Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									(203)	(195)	(204)
Other income, net									66	50	36
Income before income taxes									576	845	890
Income tax (expense) benefit									(155)	(280)	(284)
(Earnings) losses attributable to noncontrolling interest									(14)	5	(19)
Reclassification from AOCI, Net of taxes									1	1	1
Southern California Gas Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									(102)	(97)	(84)
Other income, net									36	32	30
Income before income taxes									557	493	558
Income tax (expense) benefit									(160)	(143)	(138)
Reclassification from AOCI, Net of taxes									1	1	0
Financial instruments attributable to parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, Net of taxes									7	19	10
Financial instruments attributable to parent [Member] | Southern California Gas Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, Net of taxes									0	1
Amortization of actuarial loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before taxes									18	10	14
Amortization of actuarial loss [Member] | San Diego Gas and Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, Net of taxes									1	1	1
Amortization of prior service cost [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before taxes									1	1	0
Amortization of prior service cost [Member] | Southern California Gas Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, Net of taxes									1	0	0
Pension and other postretirement benefits [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, before taxes									19	11	14
Reclassification from AOCI, Taxes									(7)	(5)	(6)
Reclassification from AOCI, Net of taxes									12	6	8
Pension and other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, Net of taxes									1	1	1
Pension and other postretirement benefits [Member] | Southern California Gas Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI, Net of taxes									1	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes									23	33	29
Income tax (expense) benefit									(6)	(6)	(4)
Net of income tax									17	27	25
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments [Member] | Interest rate and foreign exchange instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									(4)	17	18
Remeasurement of equity method investment									0	7	0
Equity earnings, net of income tax									12	5	13
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments [Member] | Interest rate instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Equity earnings, before income tax									8	10	12
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments [Member] | Interest rate instruments [Member] | San Diego Gas and Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									13	12	12
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments [Member] | Foreign exchange instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Energy-related businesses									(2)	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments [Member] | Commodity Contracts Not Subject To Rate Recovery [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Energy-related businesses									9	(6)	(14)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments attributable to Noncontrolling interests [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Earnings) losses attributable to noncontrolling interest									(10)	(15)	(15)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments attributable to Noncontrolling interests [Member] | San Diego Gas and Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Earnings) losses attributable to noncontrolling interest									(13)	(12)	(12)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments attributable to parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income/Earnings									7	12	10
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments attributable to parent [Member] | San Diego Gas and Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income/Earnings									0	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments attributable to parent [Member] | Southern California Gas Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax (expense) benefit									0	0	(1)
Net income/Earnings									0	1	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Financial instruments attributable to parent [Member] | Interest rate instruments [Member] | Southern California Gas Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense									$ 0	$ 1	$ 1