DERIVATIVE FINANCIAL INSTRUMENTS - DERIVATIVE INSTRUMENTS ON THE CONDENSED BALANCE SHEET (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	$ 156	$ 41
Additional cash collateral for commodity contracts not subject to rate recovery	2	10
Additional cash collateral for commodity contracts subject to rate recovery	16	32
Total	174	83
Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	121	82
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	121	82
Current liabilities: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	(99)	(77)
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	(99)	(77)
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	(265)	(364)
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	(265)	(364)
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	0	7
Commodity contracts not subject to rate recovery		0
Designated as Hedging Instrument [Member] | Other assets: Sundry [Member]
Derivatives designated as hedging instruments:
Interest rate and foreign exchange instruments	1	2
Commodity contracts not subject to rate recovery		0
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	(51)	(24)
Commodity contracts not subject to rate recovery		(14)
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	(143)	(228)
Commodity contracts not subject to rate recovery		0
Not Designated as Hedging Instrument [Member] | Current assets: Fixed-price contracts and other derivatives [Member]
Derivatives not designated as hedging instruments:
Foreign exchange instruments	134
Commodity contracts not subject to rate recovery	41	248
Associated offsetting commodity contracts	(26)	(242)
Associated offsetting cash collateral		0
Commodity contracts subject to rate recovery	8	37
Associated offsetting commodity contracts	(1)	(9)
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
Commodity contracts not subject to rate recovery	6	36
Associated offsetting commodity contracts	(3)	(27)
Associated offsetting cash collateral		(1)
Commodity contracts subject to rate recovery	118	73
Associated offsetting commodity contracts	(1)	(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
Commodity contracts not subject to rate recovery	(29)	(254)
Associated offsetting commodity contracts	26	242
Associated offsetting cash collateral		16
Commodity contracts subject to rate recovery	(63)	(57)
Associated offsetting commodity contracts	1	9
Associated offsetting cash collateral	17	5
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
Commodity contracts not subject to rate recovery	(4)	(28)
Associated offsetting commodity contracts	3	27
Associated offsetting cash collateral		1
Commodity contracts subject to rate recovery	(128)	(150)
Associated offsetting commodity contracts	1	1
Associated offsetting cash collateral	6	13
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	5	27
Additional cash collateral for commodity contracts not subject to rate recovery		1
Additional cash collateral for commodity contracts subject to rate recovery	15	30
Total	20	58
San Diego Gas and Electric Company [Member] | Other assets: Sundry [Member]
Derivatives not designated as hedging instruments:
Net amounts presented on the balance sheet	117	72
Additional cash collateral for commodity contracts not subject to rate recovery		0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	117	72
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	(55)	(55)
Additional cash collateral for commodity contracts not subject to rate recovery		0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(55)	(55)
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	(126)	(148)
Additional cash collateral for commodity contracts not subject to rate recovery		0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(126)	(148)
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	(12)	(13)
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	(5)	(12)
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	6	33
Associated offsetting commodity contracts	(1)	(6)
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	118	73
Associated offsetting commodity contracts	(1)	(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	(61)	(51)
Associated offsetting commodity contracts	1	6
Associated offsetting cash collateral	17	3
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	(128)	(150)
Associated offsetting commodity contracts	1	1
Associated offsetting cash collateral	6	13
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	1
Additional cash collateral for commodity contracts not subject to rate recovery		1
Additional cash collateral for commodity contracts subject to rate recovery	1	2
Total	3	4
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 not subject to rate recovery		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	(2)	(1)
Additional cash collateral for commodity contracts not subject to rate recovery		0
Additional cash collateral for commodity contracts subject to rate recovery	0	0
Total	(2)	(1)
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 not subject to rate recovery		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	4
Associated offsetting commodity contracts		(3)
Associated offsetting cash collateral		0
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
Associated offsetting commodity contracts		0
Associated offsetting cash collateral		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	(2)	(6)
Associated offsetting commodity contracts		3
Associated offsetting cash collateral		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
Associated offsetting commodity contracts		0
Associated offsetting cash collateral		$ 0