FAIR VALUE MEASUREMENTS - RECURRING FAIR VALUE MEASURES (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	$ 496	$ 508
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	54	52
Nuclear decomissioning trusts - Municipal debt securities	250	206
Nuclear decommissioning trusts - Other debt securities	217	141
Nuclear decommissioning trusts - Total debt securities	521	399
Total nuclear decommissioning trusts	1,017	907
Assets fair value disclosure, total	1,188	1,072
Liabilities fair value disclosure, total	384	441
Interest Rate and Foreign Exchange Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	7	9
Derivative Liability	217	252
Commodity contracts not subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	17	15
Effect of netting and allocation of collateral	2	9
Derivative Liability	6	27
Effect of netting and allocation of collateral		(17)
Commodity contracts subject to rate recovery [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	128	100
Effect of netting and allocation of collateral	17	32
Derivative Liability	184	197
Effect of netting and allocation of collateral	(23)	(18)
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	491	508
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	45	36
Nuclear decomissioning trusts - Municipal debt securities	0	0
Nuclear decommissioning trusts - Other debt securities	0	0
Nuclear decommissioning trusts - Total debt securities	45	36
Total nuclear decommissioning trusts	536	544
Assets fair value disclosure, total	555	574
Liabilities fair value disclosure, total	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 Asset	0	0
Derivative Liability	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 Asset	5	0
Effect of netting and allocation of collateral	2	2
Derivative Liability	0	16
Effect of netting and allocation of collateral		(17)
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	0	1
Effect of netting and allocation of collateral	12	27
Derivative Liability	23	19
Effect of netting and allocation of collateral	(23)	(18)
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nuclear decommissioning trusts - equity securities	5	0
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	9	16
Nuclear decomissioning trusts - Municipal debt securities	250	206
Nuclear decommissioning trusts - Other debt securities	217	141
Nuclear decommissioning trusts - Total debt securities	476	363
Total nuclear decommissioning trusts	481	363
Assets fair value disclosure, total	502	397
Liabilities fair value disclosure, total	230	271
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	7	9
Derivative Liability	217	252
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	12	15
Effect of netting and allocation of collateral	0	7
Derivative Liability	6	11
Effect of netting and allocation of collateral		0
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	2	3
Effect of netting and allocation of collateral	0	0
Derivative Liability	7	8
Effect of netting and allocation of collateral	0	0
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 decomissioning trusts - Municipal debt securities	0	0
Nuclear decommissioning trusts - Other debt securities	0	0
Nuclear decommissioning trusts - Total debt securities	0	0
Total nuclear decommissioning trusts	0	0
Assets fair value disclosure, total	131	101
Liabilities fair value disclosure, total	154	170
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
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
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 Asset	126	96
Effect of netting and allocation of collateral	5	5
Derivative Liability	154	170
Effect of netting and allocation of collateral	0	0
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	496	508
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	54	52
Nuclear decomissioning trusts - Municipal debt securities	250	206
Nuclear decommissioning trusts - Other debt securities	217	141
Nuclear decommissioning trusts - Total debt securities	521	399
Total nuclear decommissioning trusts	1,017	907
Assets fair value disclosure, total	1,159	1,037
Liabilities fair value disclosure, total	172	203
San Diego Gas and Electric Company [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
Effect of netting and allocation of collateral		1
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 Asset	126	99
Effect of netting and allocation of collateral	16	30
Derivative Liability	182	194
Effect of netting and allocation of collateral	(23)	(16)
San Diego Gas and Electric Company [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	13	25
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	491	508
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	45	36
Nuclear decomissioning trusts - Municipal debt securities	0	0
Nuclear decommissioning trusts - Other debt securities	0	0
Nuclear decommissioning trusts - Total debt securities	45	36
Total nuclear decommissioning trusts	536	544
Assets fair value disclosure, total	547	571
Liabilities fair value disclosure, total	0	1
San Diego Gas and Electric Company [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
Effect of netting and allocation of collateral		1
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 Asset	0	1
Effect of netting and allocation of collateral	11	25
Derivative Liability	23	17
Effect of netting and allocation of collateral	(23)	(16)
San Diego Gas and Electric Company [Member] | Level 1 [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	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	5	0
Nuclear decommissioning trusts - Debt securities issued by the U.S. Treasury and other U.S. government corporations and agencies	9	16
Nuclear decomissioning trusts - Municipal debt securities	250	206
Nuclear decommissioning trusts - Other debt securities	217	141
Nuclear decommissioning trusts - Total debt securities	476	363
Total nuclear decommissioning trusts	481	363
Assets fair value disclosure, total	481	365
Liabilities fair value disclosure, total	18	32
San Diego Gas and Electric Company [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		0
Effect of netting and allocation of collateral		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 Asset	0	2
Effect of netting and allocation of collateral	0	0
Derivative Liability	5	7
Effect of netting and allocation of collateral	0	0
San Diego Gas and Electric Company [Member] | Level 2 [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	13	25
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 decomissioning trusts - Municipal debt securities	0	0
Nuclear decommissioning trusts - Other debt securities	0	0
Nuclear decommissioning trusts - Total debt securities	0	0
Total nuclear decommissioning trusts	0	0
Assets fair value disclosure, total	131	101
Liabilities fair value disclosure, total	154	170
San Diego Gas and Electric Company [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
Effect of netting and allocation of collateral		0
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 Asset	126	96
Effect of netting and allocation of collateral	5	5
Derivative Liability	154	170
Effect of netting and allocation of collateral	0	0
San Diego Gas and Electric Company [Member] | Level 3 [Member] | Interest rate instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0	0
Southern California Gas Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	3	4
Liabilities fair value disclosure, total	2	1
Southern California Gas Company [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
Effect of netting and allocation of collateral		1
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 Asset	2	1
Effect of netting and allocation of collateral	1	2
Derivative Liability	2	3
Effect of netting and allocation of collateral		(2)
Southern California Gas Company [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	1	3
Liabilities fair value disclosure, total	0	0
Southern California Gas Company [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
Effect of netting and allocation of collateral		1
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 Asset	0	0
Effect of netting and allocation of collateral	1	2
Derivative Liability	0	2
Effect of netting and allocation of collateral		(2)
Southern California Gas Company [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure, total	2	1
Liabilities fair value disclosure, total	2	1
Southern California Gas Company [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		0
Effect of netting and allocation of collateral		0
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 Asset	2	1
Effect of netting and allocation of collateral	0	0
Derivative Liability	2	1
Effect of netting and allocation of collateral		0
Southern California Gas Company [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] | 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
Effect of netting and allocation of collateral		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 Asset	0	0
Effect of netting and allocation of collateral	0	0
Derivative Liability	$ 0	0
Effect of netting and allocation of collateral		$ 0