DERIVATIVE FINANCIAL INSTRUMENTS - BALANCE SHEET (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	$ 47,000,000	$ 41,000,000
Additional margin posted for commodity contracts not subject to rate recovery	2,000,000	10,000,000
Additional margin posted for commodity contracts subject to rate recovery	17,000,000	32,000,000
Total	66,000,000	83,000,000
Other assets: Sundry [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	105,000,000	82,000,000
Additional margin posted for commodity contracts not subject to rate recovery	0	0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	105,000,000	82,000,000
Current liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	(103,000,000)	(77,000,000)
Additional margin posted for commodity contracts not subject to rate recovery	0	0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	(103,000,000)	(77,000,000)
Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	(281,000,000)	(364,000,000)
Additional margin posted for commodity contracts not subject to rate recovery	0	0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	(281,000,000)	(364,000,000)
Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	5,000,000	7,000,000
Commodity contracts not subject to rate recovery		0
Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	2,000,000	2,000,000
Commodity contracts not subject to rate recovery		0
Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	(51,000,000)	(24,000,000)
Commodity contracts not subject to rate recovery		(14,000,000)
Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	(165,000,000)	(228,000,000)
Commodity contracts not subject to rate recovery		0
Not Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Foreign exchange instruments	0
Commodity contracts not subject to rate recovery	81,000,000	248,000,000
Associated offsetting commodity contracts not subject to rate recovery	(67,000,000)	(242,000,000)
Associated cash collateral commodity contracts not subject to rate recovery		0
Commodity contracts subject to rate recovery	28,000,000	37,000,000
Associated offsetting commodity contracts subject to rate recovery	0	(9,000,000)
Associated cash collateral commodity contracts subject to rate recovery	0	0
Not Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Foreign exchange instruments	0
Commodity contracts not subject to rate recovery	8,000,000	36,000,000
Associated offsetting commodity contracts not subject to rate recovery	(5,000,000)	(27,000,000)
Associated cash collateral commodity contracts not subject to rate recovery		(1,000,000)
Commodity contracts subject to rate recovery	101,000,000	73,000,000
Associated offsetting commodity contracts subject to rate recovery	(1,000,000)	(1,000,000)
Associated cash collateral commodity contracts subject to rate recovery	0	0
Not Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Foreign exchange instruments	(1,000,000)
Commodity contracts not subject to rate recovery	(72,000,000)	(254,000,000)
Associated offsetting commodity contracts not subject to rate recovery	67,000,000	242,000,000
Associated cash collateral commodity contracts not subject to rate recovery		16,000,000
Commodity contracts subject to rate recovery	(65,000,000)	(57,000,000)
Associated offsetting commodity contracts subject to rate recovery	0	9,000,000
Associated cash collateral commodity contracts subject to rate recovery	19,000,000	5,000,000
Not Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Foreign exchange instruments	0
Commodity contracts not subject to rate recovery	(6,000,000)	(28,000,000)
Associated offsetting commodity contracts not subject to rate recovery	5,000,000	27,000,000
Associated cash collateral commodity contracts not subject to rate recovery		1,000,000
Commodity contracts subject to rate recovery	(120,000,000)	(150,000,000)
Associated offsetting commodity contracts subject to rate recovery	1,000,000	1,000,000
Associated cash collateral commodity contracts subject to rate recovery	4,000,000	13,000,000
San Diego Gas and Electric Company [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	26,000,000	27,000,000
Additional margin posted for commodity contracts not subject to rate recovery		1,000,000
Additional margin posted for commodity contracts subject to rate recovery	16,000,000	30,000,000
Total	42,000,000	58,000,000
San Diego Gas and Electric Company [Member] | Other assets: Sundry [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	100,000,000	72,000,000
Additional margin posted for commodity contracts not subject to rate recovery		0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	100,000,000	72,000,000
San Diego Gas and Electric Company [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	(54,000,000)	(55,000,000)
Additional margin posted for commodity contracts not subject to rate recovery		0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	(54,000,000)	(55,000,000)
San Diego Gas and Electric Company [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	(118,000,000)	(148,000,000)
Additional margin posted for commodity contracts not subject to rate recovery		0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	(118,000,000)	(148,000,000)
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	0	0
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	0	0
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	(10,000,000)	(13,000,000)
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivative Instruments in Hedges, at Fair Value, Net [Abstract]
Interest rate and foreign exchange instruments	(3,000,000)	(12,000,000)
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	26,000,000	33,000,000
Associated offsetting commodity contracts subject to rate recovery	0	(6,000,000)
Associated cash collateral commodity contracts subject to rate recovery	0	0
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	101,000,000	73,000,000
Associated offsetting commodity contracts subject to rate recovery	(1,000,000)	(1,000,000)
Associated cash collateral commodity contracts subject to rate recovery	0	0
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	(63,000,000)	(51,000,000)
Associated offsetting commodity contracts subject to rate recovery	0	6,000,000
Associated cash collateral commodity contracts subject to rate recovery	19,000,000	3,000,000
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	(120,000,000)	(150,000,000)
Associated offsetting commodity contracts subject to rate recovery	1,000,000	1,000,000
Associated cash collateral commodity contracts subject to rate recovery	4,000,000	13,000,000
Southern California Gas Company [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	2,000,000	1,000,000
Additional margin posted for commodity contracts not subject to rate recovery		1,000,000
Additional margin posted for commodity contracts subject to rate recovery	1,000,000	2,000,000
Total	3,000,000	4,000,000
Southern California Gas Company [Member] | Other assets: Sundry [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	0	0
Additional margin posted for commodity contracts not subject to rate recovery		0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	0	0
Southern California Gas Company [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	(2,000,000)	(1,000,000)
Additional margin posted for commodity contracts not subject to rate recovery		0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	(2,000,000)	(1,000,000)
Southern California Gas Company [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Net amount presented on balance sheet	0	0
Additional margin posted for commodity contracts not subject to rate recovery		0
Additional margin posted for commodity contracts subject to rate recovery	0	0
Total	0	0
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	2,000,000	4,000,000
Associated offsetting commodity contracts subject to rate recovery		(3,000,000)
Associated cash collateral commodity contracts subject to rate recovery		0
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	0	0
Associated offsetting commodity contracts subject to rate recovery		0
Associated cash collateral commodity contracts subject to rate recovery		0
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	(2,000,000)	(6,000,000)
Associated offsetting commodity contracts subject to rate recovery		3,000,000
Associated cash collateral commodity contracts subject to rate recovery		2,000,000
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net [Abstract]
Commodity contracts subject to rate recovery	$ 0	0
Associated offsetting commodity contracts subject to rate recovery		0
Associated cash collateral commodity contracts subject to rate recovery		$ 0