SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - PROPERTY, PLANT, AND EQUIPMENT (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 53,928	$ 49,329
Depreciation expense	1,646	1,551	$ 1,470
Accumulated depreciation	13,925	12,877
San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	24,436	22,504
Depreciation expense	797	757	686
Accumulated depreciation	6,015	5,537
Southern California Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	21,180	19,362
Depreciation expense	649	598	$ 553
Accumulated depreciation	6,437	6,038
Natural gas operations [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,805	$ 2,534
Depreciation rates (percentage)	2.51%	2.47%	2.44%
Accumulated depreciation	$ 870	$ 832
Natural gas operations [Member] | Southern California Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 19,961	$ 18,370
Depreciation rates (percentage)	3.63%	3.60%	3.60%
Accumulated depreciation	$ 6,422	$ 6,023
Electric distribution [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 8,592	$ 7,985
Depreciation rates (percentage)	3.90%	3.94%	3.91%
Electric transmission [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 7,156	$ 6,577
Depreciation rates (percentage)	3.10%	2.79%	2.76%
Electric generation [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,440	$ 2,415
Depreciation rates (percentage)	4.56%	4.50%	4.12%
Other electric [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,743	$ 1,492
Depreciation rates (percentage)	6.92%	6.61%	6.43%
Construction work in progress [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,700	$ 1,501
Construction work in progress [Member] | Southern California Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,174	958
Other non-utility [Member] | Southern California Gas Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 45	$ 34
Depreciation rates (percentage)	3.80%	5.08%	5.39%
Accumulated depreciation	$ 15	$ 15
Other non-utility [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation	1,473	1,302
Land and land rights [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 283	278
Land and land rights [Member] | Minimum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	16 years
Land and land rights [Member] | Maximum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Land and land rights [Member] | Weighted Average [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	31 years
Generating plants [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,288	1,154
Generating plants [Member] | Minimum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	11 years
Generating plants [Member] | Maximum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	25 years
Generating plants [Member] | Weighted Average [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	22 years
LNG terminals [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,138	1,134
Estimated useful life	43 years
LNG terminals [Member] | Weighted Average [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	43 years
Pipelines and storage [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 3,482	3,596
Pipelines and storage [Member] | Minimum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Pipelines and storage [Member] | Maximum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Pipelines and storage [Member] | Weighted Average [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	44 years
Other [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 359	180
Other [Member] | Minimum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	1 year
Other [Member] | Maximum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Other [Member] | Weighted Average [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	14 years
Construction work in progress [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,514	895
Other [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 248	226
Other [Member] | Minimum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	4 years
Other [Member] | Maximum [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Other [Member] | Weighted Average [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	23 years
Total Other Operating Units And Parent [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 8,312	7,463
Plant, pipeline and other distribution assets of ecogas [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation	51	49
Plant, pipeline and other distribution assets of ecogas [Member] | Other Operating Units and Parent [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	191	178
Electricity [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation	5,145	$ 4,705
Southwest Powerlink (SWPL) transmission line [Member] | Electric transmission [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	505
Accumulated depreciation	277
Southwest Powerlink (SWPL) transmission line [Member] | Construction work in progress [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 9
Southwest Powerlink [Member] | Southwest Powerlink (SWPL) transmission line [Member] | Electric transmission [Member] | San Diego Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Ownership interest (as a percent)	88.00%