FAIR VALUE MEASUREMENTS - RECURRING FAIR VALUE MEASURES (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]
Investments at NAV	$ 9
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	491	$ 496
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	44	54
Nuclear decommissioning trusts - Municipal bonds	247	250
Nuclear decommissioning trusts - Other securities	216	217
Nuclear decommissioning trusts - Total debt securities	507	521
Total nuclear decommissioning trusts	998	1,017
Total Assets Measured at Fair Value	1,211	1,188
Total LIabilities Measured at Fair Value	304	384
Recurring [Member] | Interest rate and foreign exchange instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	46	7
Derivative liabilities	134	217
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	12	17
Effect of netting and allocation of collateral	21	2
Derivative liabilities	10	6
Recurring [Member] | Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	120	128
Effect of netting and allocation of collateral	14	17
Derivative liabilities	183	184
Effect of netting and allocation of collateral	(23)	(23)
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	486	491
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	35	45
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	35	45
Total nuclear decommissioning trusts	521	536
Total Assets Measured at Fair Value	555	555
Total LIabilities Measured at Fair Value	7	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	4	5
Effect of netting and allocation of collateral	21	2
Derivative liabilities	7	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	0	0
Effect of netting and allocation of collateral	9	12
Derivative liabilities	23	23
Effect of netting and allocation of collateral	(23)	(23)
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	5	5
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	9	9
Nuclear decommissioning trusts - Municipal bonds	247	250
Nuclear decommissioning trusts - Other securities	216	217
Nuclear decommissioning trusts - Total debt securities	472	476
Total nuclear decommissioning trusts	477	481
Total Assets Measured at Fair Value	533	502
Total LIabilities Measured at Fair Value	140	230
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	46	7
Derivative liabilities	134	217
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	8	12
Effect of netting and allocation of collateral	0	0
Derivative liabilities	3	6
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	2	2
Effect of netting and allocation of collateral	0	0
Derivative liabilities	3	7
Effect of netting and allocation of collateral	0	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
Total Assets Measured at Fair Value	123	131
Total LIabilities Measured at Fair Value	157	154
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	118	126
Effect of netting and allocation of collateral	5	5
Derivative liabilities	157	154
Effect of netting and allocation of collateral	0	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	491	496
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	44	54
Nuclear decommissioning trusts - Municipal bonds	247	250
Nuclear decommissioning trusts - Other securities	216	217
Nuclear decommissioning trusts - Total debt securities	507	521
Total nuclear decommissioning trusts	998	1,017
Total Assets Measured at Fair Value	1,128	1,159
Total LIabilities Measured at Fair Value	168	172
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	118	126
Effect of netting and allocation of collateral	12	16
Derivative liabilities	182	182
Effect of netting and allocation of collateral	(23)	(23)
San Diego Gas and Electric Company [Member] | Recurring [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	9	13
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	486	491
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	35	45
Nuclear decommissioning trusts - Municipal bonds	0	0
Nuclear decommissioning trusts - Other securities	0	0
Nuclear decommissioning trusts - Total debt securities	35	45
Total nuclear decommissioning trusts	521	536
Total Assets Measured at Fair Value	528	547
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	0	0
Effect of netting and allocation of collateral	7	11
Derivative liabilities	23	23
Effect of netting and allocation of collateral	(23)	(23)
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 1 [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
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	5	5
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	9	9
Nuclear decommissioning trusts - Municipal bonds	247	250
Nuclear decommissioning trusts - Other securities	216	217
Nuclear decommissioning trusts - Total debt securities	472	476
Total nuclear decommissioning trusts	477	481
Total Assets Measured at Fair Value	477	481
Total LIabilities Measured at Fair Value	11	18
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	0	0
Effect of netting and allocation of collateral	0	0
Derivative liabilities	2	5
Effect of netting and allocation of collateral	0	0
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 2 [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	9	13
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	123	131
Total LIabilities Measured at Fair Value	157	154
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	118	126
Effect of netting and allocation of collateral	5	5
Derivative liabilities	157	154
Effect of netting and allocation of collateral	0	0
San Diego Gas and Electric Company [Member] | Recurring [Member] | Level 3 [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	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	4	3
Total LIabilities Measured at Fair Value	1	2
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	2	2
Effect of netting and allocation of collateral	2	1
Derivative liabilities	1	2
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	1
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	0
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	2	2
Total LIabilities Measured at Fair Value	1	2
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	2	2
Effect of netting and allocation of collateral	0	0
Derivative liabilities	1	2
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