COMMITMENTS AND CONTINGENCIES - LEGAL PROCEEDINGS (Details)		1 Months Ended					3 Months Ended	9 Months Ended	12 Months Ended
	Nov. 02, 2020 plaintiff lawsuit	Nov. 30, 2019 customer	Oct. 31, 2018 plaintiff	Aug. 31, 2018 USD ($)	Jan. 31, 2017 lawsuit	Feb. 29, 2016 USD ($)	Sep. 30, 2020 USD ($) lawsuit	Sep. 30, 2020 USD ($) lawsuit	Dec. 31, 2018 claimant	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	[1]
Loss Contingencies [Line Items]
Liability for legal proceedings							$ 444,000,000	$ 444,000,000
Number of alleged violations | customer		330
Reserve for Aliso Canyon costs							268,000,000	268,000,000			$ 9,000,000
Guaymas-El Oror Segment, Sonora Pipeline [Member]
Loss Contingencies [Line Items]
Net book value of pipeline							$ 446,000,000	446,000,000
Consolidated Class Action Complaints [Member]
Loss Contingencies [Line Items]
Number of lawsuits filed | lawsuit					2
Property Class Action [Member]
Loss Contingencies [Line Items]
Number of lawsuits filed | lawsuit					1
Complaints Filed by Public Entities [Member]
Loss Contingencies [Line Items]
Number of lawsuits filed | lawsuit							3
Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Liability for legal proceedings							$ 299,000,000	299,000,000
Insurance settlements receivable							1,279,000,000	1,279,000,000
Reserve for Aliso Canyon costs							268,000,000	268,000,000			$ 9,000,000
Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Liability for legal proceedings							273,000,000	273,000,000
Net book value of Aliso Canyon facility							788,000,000	788,000,000
Estimate of costs							1,440,000,000	1,440,000,000
Payable related to natural gas leak, noncurrent							268,000,000	268,000,000
Loss contingency accrual										$ 277,000,000
Receivable related to natural gas leak							504,000,000	504,000,000
Insurance proceeds								775,000,000
Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Operation and Maintenance [Member]
Loss Contingencies [Line Items]
Loss contingency accrual							27,000,000	27,000,000		100,000,000
Loss contingency accrual, after tax							$ 22,000,000	$ 22,000,000		72,000,000
Southern California Gas Company [Member] | Shareholder Derivative Complaint [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit							4	4
Southern California Gas Company [Member] | Damages from Product Defects [Member]
Loss Contingencies [Line Items]
Maximum occupational safety and health fines						$ 75,000
Penalty assessments						233,500
Reimbursement costs						246,673
Maximum other assessments in settlement of criminal complaint						$ 6,000,000
Southern California Gas Company [Member] | Complaints Filed by Firefighters [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff			51
Southern California Gas Company [Member] | Complaints Filed by Public Entities [Member] | Funding for Environmental Projects [Member]
Loss Contingencies [Line Items]
Settlement amount payable				$ 120,000,000
Southern California Gas Company [Member] | Complaints Filed by Public Entities [Member] | Civil Penalties [Member]
Loss Contingencies [Line Items]
Settlement amount payable				$ 21,000,000
Sempra Mexico [Member] | ECA LNG Regasification facility [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit							4	4
Number of plaintiffs | claimant									2
Subsequent Event [Member] | Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	394
Number of plaintiffs | plaintiff	36,000
Subsequent Event [Member] | Energy Future Holdings Corp. [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	275
Number of lawsuits filed | lawsuit	182
Deferred Credits and Other [Member] | Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Reserve for Aliso Canyon costs							$ 7,000,000	$ 7,000,000
Insurance Receivable [Member] | Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Loss contingency accrual										$ 177,000,000

[1] Derived from audited financial statements.