FAIR VALUE MEASUREMENTS - RECURRING FAIR VALUE MEASURES (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at NAV		$ 5
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	$ 389	509
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	49	57
Nuclear decommissioning trusts - Municipal bonds	335	282
Nuclear decommissioning trusts - Other securities	271	226
Nuclear decommissioning trusts - Total debt securities	655	565
Total nuclear decommissioning trusts	1,044	1,074
Support Agreement, net of related guarantee fees	6
Total Assets Measured at Fair Value	1,227	1,285
Total Liabilities Measured at Fair Value	295	245
Recurring [Member] | Interest rate and foreign exchange instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8	24
Derivative liabilities	219	157
Recurring [Member] | Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	5	11
Effect of netting and allocation of collateral	41	43
Derivative liabilities	17	17
Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	99	108
Effect of netting and allocation of collateral	24	25
Derivative liabilities	59	85
Effect of netting and allocation of collateral		(14)
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	382	503
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	26	46
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	26	46
Total nuclear decommissioning trusts	408	549
Support Agreement, net of related guarantee fees	0
Total Assets Measured at Fair Value	476	608
Total Liabilities Measured at Fair Value	0	0
Recurring [Member] | Level 1 [Member] | Interest rate and foreign exchange instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Recurring [Member] | Level 1 [Member] | Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Effect of netting and allocation of collateral	41	43
Derivative liabilities	0	0
Recurring [Member] | Level 1 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	9	5
Effect of netting and allocation of collateral	18	11
Derivative liabilities	0	14
Effect of netting and allocation of collateral		(14)
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	7	6
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	23	11
Nuclear decommissioning trusts - Municipal bonds	335	282
Nuclear decommissioning trusts - Other securities	271	226
Nuclear decommissioning trusts - Total debt securities	629	519
Total nuclear decommissioning trusts	636	525
Support Agreement, net of related guarantee fees	0
Total Assets Measured at Fair Value	653	576
Total Liabilities Measured at Fair Value	242	178
Recurring [Member] | Level 2 [Member] | Interest rate and foreign exchange instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	8	24
Derivative liabilities	219	157
Recurring [Member] | Level 2 [Member] | Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	5	11
Effect of netting and allocation of collateral	0	0
Derivative liabilities	17	17
Recurring [Member] | Level 2 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4	8
Effect of netting and allocation of collateral	0	8
Derivative liabilities	6	4
Effect of netting and allocation of collateral		0
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	0	0
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0	0
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	0	0
Total nuclear decommissioning trusts	0	0
Support Agreement, net of related guarantee fees	6
Total Assets Measured at Fair Value	98	101
Total Liabilities Measured at Fair Value	53	67
Recurring [Member] | Level 3 [Member] | Interest rate and foreign exchange instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Recurring [Member] | Level 3 [Member] | Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Effect of netting and allocation of collateral	0	0
Derivative liabilities	0	0
Recurring [Member] | Level 3 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	86	95
Effect of netting and allocation of collateral	6	6
Derivative liabilities	53	67
Effect of netting and allocation of collateral		0
San Diego Gas and Electric Company [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	389	509
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	49	57
Nuclear decommissioning trusts - Municipal bonds	335	282
Nuclear decommissioning trusts - Other securities	271	226
Nuclear decommissioning trusts - Total debt securities	655	565
Total nuclear decommissioning trusts	1,044	1,074
Total Assets Measured at Fair Value	1,162	1,189
Total Liabilities Measured at Fair Value	53	67
San Diego Gas and Electric Company [Member] | Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	96	99
Effect of netting and allocation of collateral	22	16
Derivative liabilities	53	81
Effect of netting and allocation of collateral		(14)
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	382	503
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	26	46
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	26	46
Total nuclear decommissioning trusts	408	549
Total Assets Measured at Fair Value	433	560
Total Liabilities Measured at Fair Value	0	0
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 1 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	9	1
Effect of netting and allocation of collateral	16	10
Derivative liabilities	0	14
Effect of netting and allocation of collateral		(14)
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	7	6
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	23	11
Nuclear decommissioning trusts - Municipal bonds	335	282
Nuclear decommissioning trusts - Other securities	271	226
Nuclear decommissioning trusts - Total debt securities	629	519
Total nuclear decommissioning trusts	636	525
Total Assets Measured at Fair Value	637	528
Total Liabilities Measured at Fair Value	0	0
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 2 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1	3
Effect of netting and allocation of collateral	0	0
Derivative liabilities	0	0
Effect of netting and allocation of collateral		0
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	0	0
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	0	0
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	0	0
Total nuclear decommissioning trusts	0	0
Total Assets Measured at Fair Value	92	101
Total Liabilities Measured at Fair Value	53	67
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 3 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	86	95
Effect of netting and allocation of collateral	6	6
Derivative liabilities	53	67
Effect of netting and allocation of collateral		0
Southern California Gas Company [Member] | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	5	18
Total Liabilities Measured at Fair Value	6	4
Southern California Gas Company [Member] | Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	3	9
Effect of netting and allocation of collateral	2	9
Derivative liabilities	6	4
Southern California Gas Company [Member] | Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	2	5
Total Liabilities Measured at Fair Value	0	0
Southern California Gas Company [Member] | Recurring [Member] | Level 1 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	4
Effect of netting and allocation of collateral	2	1
Derivative liabilities	0	0
Southern California Gas Company [Member] | Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	3	13
Total Liabilities Measured at Fair Value	6	4
Southern California Gas Company [Member] | Recurring [Member] | Level 2 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	3	5
Effect of netting and allocation of collateral	0	8
Derivative liabilities	6	4
Southern California Gas Company [Member] | Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	0	0
Total Liabilities Measured at Fair Value	0	0
Southern California Gas Company [Member] | Recurring [Member] | Level 3 [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Effect of netting and allocation of collateral	0	0
Derivative liabilities	$ 0	$ 0