FAIR VALUE MEASUREMENTS - RECURRING FAIR VALUE MEASURES (Details) - USD ($) $ in Millions	Dec. 31, 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]
Alternative investment		$ 5
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	$ 1,025	1,074
Support Agreement, net of related guarantee fees	7
Assets fair value disclosure, total	1,240	1,285
Support Agreement, net of related guarantee fees	4
Liabilities fair value disclosure, total	264	245
Fair Value, Recurring [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	364	509
Fair Value, Recurring [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	65	57
Fair Value, Recurring [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	326	282
Fair Value, Recurring [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	270	226
Fair Value, Recurring [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	661	565
Fair Value, Recurring [Member] | Interest Rate and Foreign Exchange Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	25	24
Derivative liability	186	157
Fair Value, Recurring [Member] | Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	4	11
Effect of netting and allocation of collateral	21	43
Derivative liability	16	17
Fair Value, Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	128	108
Effect of netting and allocation of collateral	30	25
Derivative liability	58	85
Effect of netting and allocation of collateral		(14)
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	399	549
Support Agreement, net of related guarantee fees	0
Assets fair value disclosure, total	445	608
Support Agreement, net of related guarantee fees	0
Liabilities fair value disclosure, total	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	358	503
Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	41	46
Fair Value, Recurring [Member] | Level 1 [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	41	46
Fair Value, 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 asset	0	0
Derivative liability	0	0
Fair Value, 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 asset	0	0
Effect of netting and allocation of collateral	21	43
Derivative liability	0	0
Fair Value, 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 asset	6	5
Effect of netting and allocation of collateral	19	11
Derivative liability	0	14
Effect of netting and allocation of collateral		(14)
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	626	525
Support Agreement, net of related guarantee fees	0
Assets fair value disclosure, total	661	576
Support Agreement, net of related guarantee fees	0
Liabilities fair value disclosure, total	208	178
Fair Value, Recurring [Member] | Level 2 [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	6	6
Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	24	11
Fair Value, Recurring [Member] | Level 2 [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	326	282
Fair Value, Recurring [Member] | Level 2 [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	270	226
Fair Value, Recurring [Member] | Level 2 [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	620	519
Fair Value, 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 asset	25	24
Derivative liability	186	157
Fair Value, 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 asset	4	11
Effect of netting and allocation of collateral	0	0
Derivative liability	16	17
Fair Value, 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 asset	1	8
Effect of netting and allocation of collateral	5	8
Derivative liability	6	4
Effect of netting and allocation of collateral		0
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Support Agreement, net of related guarantee fees	7
Assets fair value disclosure, total	134	101
Support Agreement, net of related guarantee fees	4
Liabilities fair value disclosure, total	56	67
Fair Value, Recurring [Member] | Level 3 [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Fair Value, 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 asset	0	0
Derivative liability	0	0
Fair Value, 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 asset	0	0
Effect of netting and allocation of collateral	0	0
Derivative liability	0	0
Fair Value, 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 asset	121	95
Effect of netting and allocation of collateral	6	6
Derivative liability	52	67
Effect of netting and allocation of collateral		0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	1,025	1,074
Assets fair value disclosure, total	1,175	1,189
Liabilities fair value disclosure, total	52	67
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	364	509
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	65	57
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	326	282
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	270	226
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	661	565
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	126	99
Effect of netting and allocation of collateral	24	16
Derivative liability	52	81
Effect of netting and allocation of collateral		(14)
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	399	549
Assets fair value disclosure, total	422	560
Liabilities fair value disclosure, total	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	358	503
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	41	46
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	41	46
San Diego Gas and Electric Company [Member] | Fair Value, 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 asset	5	1
Effect of netting and allocation of collateral	18	10
Derivative liability	0	14
Effect of netting and allocation of collateral		(14)
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	626	525
Assets fair value disclosure, total	626	528
Liabilities fair value disclosure, total	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	6	6
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	24	11
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	326	282
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	270	226
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	620	519
San Diego Gas and Electric Company [Member] | Fair Value, 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 asset	0	3
Effect of netting and allocation of collateral	0	0
Derivative liability	0	0
Effect of netting and allocation of collateral		0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
Assets fair value disclosure, total	127	101
Liabilities fair value disclosure, total	52	67
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Equity Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Other securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total nuclear decommissioning trusts	0	0
San Diego Gas and Electric Company [Member] | Fair Value, 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 asset	121	95
Effect of netting and allocation of collateral	6	6
Derivative liability	52	67
Effect of netting and allocation of collateral		0
Southern California Gas Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	8	18
Liabilities fair value disclosure, total	6	4
Southern California Gas Company [Member] | Fair Value, Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	2	9
Effect of netting and allocation of collateral	6	9
Derivative liability	6	4
Southern California Gas Company [Member] | Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	2	5
Liabilities fair value disclosure, total	0	0
Southern California Gas Company [Member] | Fair Value, 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 asset	1	4
Effect of netting and allocation of collateral	1	1
Derivative liability	0	0
Southern California Gas Company [Member] | Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	6	13
Liabilities fair value disclosure, total	6	4
Southern California Gas Company [Member] | Fair Value, 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 asset	1	5
Effect of netting and allocation of collateral	5	8
Derivative liability	6	4
Southern California Gas Company [Member] | Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	0	0
Liabilities fair value disclosure, total	0	0
Southern California Gas Company [Member] | Fair Value, 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 asset	0	0
Effect of netting and allocation of collateral	0	0
Derivative liability	$ 0	$ 0