FAIR VALUE MEASUREMENTS - FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates, allowance for credit losses	$ 3
Unamortized discount and debt issuance costs	263	$ 225
Finance lease obligations	1,335	1,289
Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	620	742
Long-term amounts due to unconsolidated affiliate	271	195
Total long-term debt	23,588	21,247
Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	649	759
Long-term amounts due to unconsolidated affiliate	280	184
Total long-term debt	26,105	22,664
Fair value [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	0	0
Long-term amounts due to unconsolidated affiliate	0	0
Total long-term debt	0	0
Fair value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	649	759
Long-term amounts due to unconsolidated affiliate	280	184
Total long-term debt	26,105	22,638
Fair value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term amounts due from unconsolidated affiliates	0	0
Long-term amounts due to unconsolidated affiliate	0	0
Total long-term debt	0	26
San Diego Gas and Electric Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized discount and debt issuance costs	59	48
Finance lease obligations	1,278	1,270
San Diego Gas and Electric Company [Member] | Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	6,505	5,140
San Diego Gas and Electric Company [Member] | Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	7,481	5,662
San Diego Gas and Electric Company [Member] | Fair value [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	0	0
San Diego Gas and Electric Company [Member] | Fair value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	7,481	5,662
San Diego Gas and Electric Company [Member] | Fair value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	0	0
Southern California Gas Company [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized discount and debt issuance costs	41	34
Finance lease obligations	57	19
Southern California Gas Company [Member] | Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	4,759	3,809
Southern California Gas Company [Member] | Fair value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	5,573	4,189
Southern California Gas Company [Member] | Fair value [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	0	0
Southern California Gas Company [Member] | Fair value [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	5,573	4,189
Southern California Gas Company [Member] | Fair value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	$ 0	$ 0