SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ 12,951
Amounts reclassified from AOCI		19	$ 18		$ 18
Ending Balance		12,670	12,951	[1]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Sale of noncontrolling interests, net of offering costs		196	1,701
San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	5,641
Amounts reclassified from AOCI		1	1		1
Ending Balance		5,598	5,641	[1]
Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	3,510
Amounts reclassified from AOCI		1	1		0
Ending Balance		3,907	3,510	[1]
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(527)	(582)		(322)
OCI before reclassifications		107	42		(260)
Amounts reclassified from AOCI		0	13		0
Total other comprehensive income (loss)		107	55		(260)
Ending Balance		(420)	(527)		(582)
Financial instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(125)	(137)		(90)
OCI before reclassifications		(4)	(7)		(57)
Amounts reclassified from AOCI		7	19		10
Total other comprehensive income (loss)		3	12		(47)
Ending Balance		(122)	(125)		(137)
Financial instruments [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(13)	(14)		(14)
OCI before reclassifications			0		0
Amounts reclassified from AOCI		0	1
Total other comprehensive income (loss)		0	1		0
Ending Balance		(13)	(13)		(14)
Pension and other postretirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(96)	(87)		(85)
OCI before reclassifications		0	(15)		(10)
Amounts reclassified from AOCI		12	6		8
Total other comprehensive income (loss)		12	(9)		(2)
Ending Balance		(84)	(96)		(87)
Pension and other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(8)	(8)		(12)
OCI before reclassifications		(1)	(1)		3
Amounts reclassified from AOCI		1	1		1
Total other comprehensive income (loss)		0	0		4
Ending Balance		(8)	(8)		(8)
Pension and other postretirement benefits [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(9)	(5)		(4)
OCI before reclassifications			(4)		(1)
Amounts reclassified from AOCI		1	0
Total other comprehensive income (loss)		1	(4)		(1)
Ending Balance		(8)	(9)		(5)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(748)	(806)		(497)
OCI before reclassifications		103	20		(327)
Amounts reclassified from AOCI		19	38		18
Total other comprehensive income (loss)		122	58		(309)
Ending Balance		(626)	(748)		(806)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Sale of noncontrolling interests, net of offering costs			20
Accumulated other comprehensive income (loss) [Member] | San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(8)	(8)		(12)
OCI before reclassifications		(1)	(1)		3
Amounts reclassified from AOCI		1	1		1
Total other comprehensive income (loss)		0	0		4
Ending Balance		(8)	(8)		(8)
Accumulated other comprehensive income (loss) [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(22)	(19)		(18)
OCI before reclassifications			(4)		(1)
Amounts reclassified from AOCI		1	1
Total other comprehensive income (loss)		1	(3)		(1)
Ending Balance		$ (21)	$ (22)		$ (19)

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