SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	$ 19,929
AOCI, ending balance	23,373	$ 19,929
San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	7,100
AOCI, ending balance	7,730	7,100
Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	4,748
AOCI, ending balance	5,144	4,748
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(607)	(564)	$ (420)
OCI before reclassifications	(102)	(43)	(144)
Amounts reclassified from AOCI	645	0	0
Total other comprehensive income (loss)	543	(43)	(144)
AOCI, ending balance	(64)	(607)	(564)
Foreign currency translation adjustments [Member] | Sempra Mexico [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI associated with noncontrolling interests	4
Foreign currency translation adjustments [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		0	0
AOCI, ending balance			0
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(215)	(82)	(122)
OCI before reclassifications	(163)	(116)	40
Amounts reclassified from AOCI	47	8	3
Total other comprehensive income (loss)	(116)	(108)	43
AOCI, ending balance	(331)	(215)	(82)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Sempra Mexico [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI associated with noncontrolling interests	3
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(25)	(3)
AOCI, ending balance			(25)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(13)	(12)	(13)
OCI before reclassifications	0	0	0
Amounts reclassified from AOCI	0	1	1
Total other comprehensive income (loss)	0	1	1
AOCI, ending balance	(13)	(13)	(12)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Southern California Gas Company [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(2)
AOCI, ending balance			(2)
Pension and other postretirement benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(117)	(118)	(84)
OCI before reclassifications	(26)	(18)	(52)
Amounts reclassified from AOCI	38	36	18
Total other comprehensive income (loss)	12	18	(34)
AOCI, ending balance	(105)	(117)	(118)
Pension and other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	3
Pension and other postretirement benefits [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI		4
Pension and other postretirement benefits [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(17)	0
AOCI, ending balance			(17)
Pension and other postretirement benefits [Member] | San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(16)	(10)	(8)
OCI before reclassifications	(4)	(5)	(6)
Amounts reclassified from AOCI	10	1	4
Total other comprehensive income (loss)	6	(4)	(2)
AOCI, ending balance	(10)	(16)	(10)
Pension and other postretirement benefits [Member] | San Diego Gas and Electric Company [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	6
Pension and other postretirement benefits [Member] | San Diego Gas and Electric Company [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(2)
AOCI, ending balance			(2)
Pension and other postretirement benefits [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(10)	(8)	(8)
OCI before reclassifications	(10)	(4)	(1)
Amounts reclassified from AOCI	2	4	1
Total other comprehensive income (loss)	(8)	0	0
AOCI, ending balance	(18)	(10)	(8)
Pension and other postretirement benefits [Member] | Southern California Gas Company [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(2)
AOCI, ending balance			(2)
Accumulated other comprehensive income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(939)	(764)	(626)
OCI before reclassifications	(291)	(177)	(156)
Amounts reclassified from AOCI	730	44	21
Total other comprehensive income (loss)	439	(133)	(135)
AOCI, ending balance	(500)	(939)	(764)
Accumulated other comprehensive income (loss) [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(42)	(3)
AOCI, ending balance			(42)
Accumulated other comprehensive income (loss) [Member] | San Diego Gas and Electric Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(16)	(10)	(8)
OCI before reclassifications	(4)	(5)	(6)
Amounts reclassified from AOCI	10	1	4
Total other comprehensive income (loss)	6	(4)	(2)
AOCI, ending balance	(10)	(16)	(10)
Accumulated other comprehensive income (loss) [Member] | San Diego Gas and Electric Company [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		(2)
AOCI, ending balance			(2)
Accumulated other comprehensive income (loss) [Member] | Southern California Gas Company [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance	(23)	(20)	(21)
OCI before reclassifications	(10)	(4)	(1)
Amounts reclassified from AOCI	2	5	2
Total other comprehensive income (loss)	(8)	1	1
AOCI, ending balance	$ (31)	(23)	(20)
Accumulated other comprehensive income (loss) [Member] | Southern California Gas Company [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, beginning balance		$ (4)
AOCI, ending balance			$ (4)