FAIR VALUE MEASUREMENTS - RECURRING FAIR VALUE MEASURES (Details) - Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	$ 356	$ 364
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	52	65
Nuclear decommissioning trusts - Municipal bonds	320	326
Nuclear decommissioning trusts - Other securities	270	270
Nuclear decommissioning trusts - Total debt securities	642	661
Total nuclear decommissioning trusts	998	1,025
Support Agreement, net of related guarantee fees	7	7
Total Assets Measured at Fair Value	1,241	1,240
Support Agreement, net of related guarantee fees	2	4
Total Liabilities Measured at Fair Value	299	264
Interest rate and foreign exchange instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	6	25
Derivative liabilities	176	186
Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	31	4
Effect of netting and allocation of collateral	47	21
Derivative liabilities	81	16
Effect of netting and allocation of collateral	(11)
Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	122	128
Effect of netting and allocation of collateral	30	30
Derivative liabilities	51	58
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	350	358
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	40	41
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	40	41
Total nuclear decommissioning trusts	390	399
Support Agreement, net of related guarantee fees	0	0
Total Assets Measured at Fair Value	493	445
Support Agreement, net of related guarantee fees	0	0
Total Liabilities Measured at Fair Value	0	0
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
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	47	21
Derivative liabilities	0	0
Effect of netting and allocation of collateral	0
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	32	6
Effect of netting and allocation of collateral	24	19
Derivative liabilities	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	6	6
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	12	24
Nuclear decommissioning trusts - Municipal bonds	320	326
Nuclear decommissioning trusts - Other securities	270	270
Nuclear decommissioning trusts - Total debt securities	602	620
Total nuclear decommissioning trusts	608	626
Support Agreement, net of related guarantee fees	0	0
Total Assets Measured at Fair Value	647	661
Support Agreement, net of related guarantee fees	0	0
Total Liabilities Measured at Fair Value	281	208
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	6	25
Derivative liabilities	176	186
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	31	4
Effect of netting and allocation of collateral	0	0
Derivative liabilities	81	16
Effect of netting and allocation of collateral	(11)
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	2	1
Effect of netting and allocation of collateral	0	5
Derivative liabilities	35	6
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	7	7
Total Assets Measured at Fair Value	101	134
Support Agreement, net of related guarantee fees	2	4
Total Liabilities Measured at Fair Value	18	56
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
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
Effect of netting and allocation of collateral	0
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	88	121
Effect of netting and allocation of collateral	6	6
Derivative liabilities	16	52
San Diego Gas and Electric Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	356	364
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	52	65
Nuclear decommissioning trusts - Municipal bonds	320	326
Nuclear decommissioning trusts - Other securities	270	270
Nuclear decommissioning trusts - Total debt securities	642	661
Total nuclear decommissioning trusts	998	1,025
Total Assets Measured at Fair Value	1,146	1,175
Total Liabilities Measured at Fair Value	17	52
San Diego Gas and Electric Company [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	120	126
Effect of netting and allocation of collateral	28	24
Derivative liabilities	17	52
San Diego Gas and Electric Company [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	350	358
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	40	41
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	40	41
Total nuclear decommissioning trusts	390	399
Total Assets Measured at Fair Value	444	422
Total Liabilities Measured at Fair Value	0	0
San Diego Gas and Electric Company [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	32	5
Effect of netting and allocation of collateral	22	18
Derivative liabilities	0	0
San Diego Gas and Electric Company [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	6	6
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	12	24
Nuclear decommissioning trusts - Municipal bonds	320	326
Nuclear decommissioning trusts - Other securities	270	270
Nuclear decommissioning trusts - Total debt securities	602	620
Total nuclear decommissioning trusts	608	626
Total Assets Measured at Fair Value	608	626
Total Liabilities Measured at Fair Value	1	0
San Diego Gas and Electric Company [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	0	0
Effect of netting and allocation of collateral	0	0
Derivative liabilities	1	0
San Diego Gas and Electric Company [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	94	127
Total Liabilities Measured at Fair Value	16	52
San Diego Gas and Electric Company [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	88	121
Effect of netting and allocation of collateral	6	6
Derivative liabilities	16	52
Southern California Gas Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	4	8
Total Liabilities Measured at Fair Value	34	6
Southern California Gas Company [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	2	2
Effect of netting and allocation of collateral	2	6
Derivative liabilities	34	6
Southern California Gas Company [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	2	2
Total Liabilities Measured at Fair Value	0	0
Southern California Gas Company [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	1
Effect of netting and allocation of collateral	2	1
Derivative liabilities	0	0
Southern California Gas Company [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets Measured at Fair Value	2	6
Total Liabilities Measured at Fair Value	34	6
Southern California Gas Company [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	2	1
Effect of netting and allocation of collateral	0	5
Derivative liabilities	34	6
Southern California Gas Company [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] | 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