GENERAL INFORMATION AND OTHER FINANCIAL DATA - DUE TO DUE FROM AFFILIATES (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)		Sep. 30, 2020 MXN ($)
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	$ 46,000,000	$ 32,000,000	[1]
Due from unconsolidated affiliates - noncurrent	617,000,000	742,000,000	[1]
Due to unconsolidated affiliates, current	(6,000,000)	(5,000,000)	[1]
Due to unconsolidated affiliates - noncurrent	(271,000,000)	(195,000,000)	[1]
Maximum borrowing capacity	$ 6,685,000,000
TAG Pipeline Norte [Member]
Related Party Transaction [Line Items]
Interest rate on due from affiliate, noncurrent	3.16%
TAG Pipeline Norte [Member] | LIBOR [Member]
Related Party Transaction [Line Items]
Spread on variable rate (as a percent)	2.90%
ESJ joint venture [Member]
Related Party Transaction [Line Items]
Note receivable, term	10 years
ESJ joint venture [Member] | LIBOR [Member]
Related Party Transaction [Line Items]
Spread on variable rate (as a percent)	1.96%
Interest rate on due from affiliate, noncurrent	2.12%
San Diego Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	$ 3,000,000	0
Due to unconsolidated affiliates, current	(61,000,000)	(53,000,000)	[1]
Maximum borrowing capacity	1,500,000,000
San Diego Gas and Electric Company [Member] | Due to/from Sempra Energy [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates, current	(56,000,000)	(37,000,000)
Income taxes due (to) from Sempra Energy	25,000,000	130,000,000
San Diego Gas and Electric Company [Member] | Due to/from SoCalGas [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	2,000,000	0
Due to unconsolidated affiliates, current	0	(10,000,000)
San Diego Gas and Electric Company [Member] | Due to/from Other affiliates [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	1,000,000	0
Due to unconsolidated affiliates, current	(5,000,000)	(6,000,000)
Southern California Gas Company [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	1,000,000	11,000,000	[1]
Due to unconsolidated affiliates, current	(101,000,000)	(47,000,000)	[1]
Maximum borrowing capacity	750,000,000
Southern California Gas Company [Member] | Due to/from Sempra Energy [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates, current	(49,000,000)	(45,000,000)
Income taxes due (to) from Sempra Energy	20,000,000	152,000,000
Southern California Gas Company [Member] | Due to/from Other affiliates [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	1,000,000	1,000,000
Due to unconsolidated affiliates, current	0	(2,000,000)
Southern California Gas Company [Member] | Due to/from SDG&E
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	0	10,000,000
Due to unconsolidated affiliates, current	(2,000,000)	0
Southern California Gas Company [Member] | Pacific Enterprises [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates, current	(50,000,000)	0
IEnova Pipelines [Member] | ESJ joint venture [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - current	25,000,000
Sempra Mexico [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates - noncurrent	(271,000,000)	(195,000,000)
Sempra Mexico [Member] | IMG [Member]
Related Party Transaction [Line Items]
Due from unconsolidated affiliates - noncurrent	617,000,000	742,000,000
Due from affiliates, allowance for credit loss	3,000,000
Maximum borrowing capacity	641,000,000			$ 14,200,000,000
Accrued interest receivable	$ 2,000,000
Sempra Mexico [Member] | IMG [Member] | Interbank Equilibrium Rate [Member]
Related Party Transaction [Line Items]
Spread on variable rate (as a percent)	2.20%
Interest rate on due from affiliate, noncurrent	6.75%
Sempra Mexico [Member] | TAG Pipeline Norte [Member]
Related Party Transaction [Line Items]
Stated rate of debt (as a percent)	5.50%			5.50%
Sempra Mexico [Member] | TAG JV Notes [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates - noncurrent	$ (163,000,000)	(156,000,000)
Stated rate of debt (as a percent)	5.74%			5.74%
Other Long term Debt Currently Through December 2021 [Member] | Sempra Mexico [Member] | TAG Pipeline Norte [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates - noncurrent	$ (41,000,000)	(39,000,000)
Other Long term Debt Currently Through January 2024 [Member] | Sempra Mexico [Member] | TAG Pipeline Norte [Member]
Related Party Transaction [Line Items]
Due to unconsolidated affiliates - noncurrent	$ (67,000,000)	$ 0

[1] Derived from audited financial statements.