COMMITMENTS AND CONTINGENCIES - LEGAL PROCEEDINGS (Details)					1 Months Ended		3 Months Ended
	May 03, 2018 plaintiff lawsuit	Jul. 19, 2017 Bcf	Mar. 13, 2017	Mar. 31, 2016 t	Jan. 31, 2017 lawsuit	Sep. 30, 2016 USD ($)	Mar. 31, 2018 USD ($) Bcf lawsuit	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	[1]	Oct. 21, 2016 t
Loss Contingencies [Line Items]
Liability for legal proceedings							$ 144,000,000
Percent of arbitration expenses reduction of award			95.00%
Reserve for Aliso Canyon costs							122,000,000		$ 84,000,000
Insurance receivable for Aliso Canyon costs							$ 447,000,000		418,000,000
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
San Diego Gas and Electric Company [Member]
Loss Contingencies [Line Items]
Liability for legal proceedings							$ 3,000,000
San Diego Gas and Electric Company [Member] | Wildfire [Member]
Loss Contingencies [Line Items]
Write-off of wildfire regulatory asset								$ 351,000,000
After-tax charge for nonrecovery of CPUC regulatory assets								$ 208,000,000
Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Liability for legal proceedings							90,000,000
Insurance Settlements Receivable							928,000,000
Reserve for Aliso Canyon costs							122,000,000		84,000,000
Insurance receivable for Aliso Canyon costs							447,000,000		$ 418,000,000
Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Liability for legal proceedings							85,000,000
Loss contingency accrual							$ 954,000,000
Percent of Loss Accrual Allocated to Temporary Relocation Program							60.00%
Reserve for Aliso Canyon costs							$ 122,000,000
Receivable related to natural gas leak							447,000,000
Insurance proceeds							$ 481,000,000
Period of required climate reductions				20 years
Period of required regulatory climate reductions				100 years
Target emissions level (in metric tons) | t				9,000,000
Loss Contingency, Total Actual Emissions, Floor (in metric tons) | t											90,350
Loss Contingency, Total Actual Emissions, Ceiling (in metric tons) | t											108,950
Mitigation requirements (in metric tons) | t											109,000
Amount of natural gas released | Bcf							4.62
Required working gas target | Bcf		23.6
Required working gas minimum | Bcf		14.8
Storage facility capacity | Bcf							86
Proportion of total gas storage capacity (percentage)		28.00%					63.00%
Net book value of Aliso Canyon facility							$ 656,000,000
Construction work in progress of new compressor station							259,000,000
Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	381
Number of plaintiffs | plaintiff	48,000
Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Liability insurance coverage							1,200,000,000
Environmental mitigation period				5 years
Required working gas target | Bcf		0
Southern California Gas Company [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Liability insurance coverage							$ 1,400,000,000
Environmental mitigation period				10 years
Required working gas target | Bcf		24.6
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
Maximum other assessments in settlement of criminal complaint						$ 6,000,000

[1] Derived from audited financial statements.