DERIVATIVE FINANCIAL INSTRUMENTS - DERIVATIVE INSTRUMENTS ON THE CONDENSED BALANCE SHEET (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	$ 76	$ 47
Additional cash collateral for commodity contracts not subject to rate recovery	21	2
Additional cash collateral for commodity contracts subject to rate recovery	14	17
Total	111	66
Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	102	105
Additional cash collateral for commodity contracts not subject to rate recovery	0	0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	102	105
Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	(63)	(103)
Additional cash collateral for commodity contracts not subject to rate recovery	0	0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(63)	(103)
Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	(241)	(281)
Additional cash collateral for commodity contracts not subject to rate recovery	0	0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(241)	(281)
Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives designated as hedging instruments:
Interest rate and foreign exchange instruments	1	5
Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivatives designated as hedging instruments:
Interest rate and foreign exchange instruments	2	2
Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives designated as hedging instruments:
Interest rate and foreign exchange instruments	(12)	(51)
Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives designated as hedging instruments:
Interest rate and foreign exchange instruments	(122)	(165)
Not Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Foreign exchange instruments	43	0
Commodity contracts not subject to rate recovery	64	81
Associated offsetting commodity contracts	(54)	(67)
Commodity contracts subject to rate recovery	22	28
Associated offsetting commodity contracts		0
Associated offsetting cash collateral	0	0
Not Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Foreign exchange instruments	0	0
Commodity contracts not subject to rate recovery	10	8
Associated offsetting commodity contracts	(8)	(5)
Commodity contracts subject to rate recovery	98	101
Associated offsetting commodity contracts		(1)
Associated offsetting cash collateral	0	0
Not Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Foreign exchange instruments	0	(1)
Commodity contracts not subject to rate recovery	(61)	(72)
Associated offsetting commodity contracts	54	67
Commodity contracts subject to rate recovery	(60)	(65)
Associated offsetting commodity contracts		0
Associated offsetting cash collateral	16	19
Not Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Foreign exchange instruments	0	0
Commodity contracts not subject to rate recovery	(11)	(6)
Associated offsetting commodity contracts	8	5
Commodity contracts subject to rate recovery	(123)	(120)
Associated offsetting commodity contracts		1
Associated offsetting cash collateral	7	4
San Diego Gas and Electric Company [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	20	26
Additional cash collateral for commodity contracts subject to rate recovery	12	16
Total	32	42
San Diego Gas and Electric Company [Member] | Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	98	100
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	98	100
San Diego Gas and Electric Company [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	(51)	(54)
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(51)	(54)
San Diego Gas and Electric Company [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	(117)	(118)
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(117)	(118)
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives designated as hedging instruments:
Interest rate instruments	0	0
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivatives designated as hedging instruments:
Interest rate instruments	0	0
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives designated as hedging instruments:
Interest rate instruments	(8)	(10)
San Diego Gas and Electric Company [Member] | Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives designated as hedging instruments:
Interest rate instruments	(1)	(3)
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	20	26
Associated offsetting commodity contracts		0
Associated offsetting cash collateral	0	0
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	98	101
Associated offsetting commodity contracts		(1)
Associated offsetting cash collateral	0	0
San Diego Gas and Electric Company [Member] | Not Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	(59)	(63)
Associated offsetting commodity contracts		0
Associated offsetting cash collateral	16	19
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]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	(123)	(120)
Associated offsetting commodity contracts		1
Associated offsetting cash collateral	7	4
Southern California Gas Company [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	2	2
Additional cash collateral for commodity contracts subject to rate recovery	2	1
Total	4	3
Southern California Gas Company [Member] | Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	0	0
Additional cash collateral 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]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	(1)	(2)
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(1)	(2)
Southern California Gas Company [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	0	0
Additional cash collateral 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]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	2	2
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	0	0
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	(1)	(2)
Southern California Gas Company [Member] | Not Designated as Hedging Instrument [Member] | Deferred credits and other liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Commodity contracts subject to rate recovery	$ 0	$ 0