COMMITMENTS AND CONTINGENCIES - LOSS ON CONTINGENCIES (Details) £ in Millions					1 Months Ended			12 Months Ended
	Feb. 22, 2018 plaintiff lawsuit	Jul. 19, 2017 Bcf	Mar. 13, 2017	Mar. 31, 2016 t	Feb. 28, 2017 USD ($)	Jan. 31, 2017 lawsuit	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) Bcf appeal	Dec. 31, 2016 USD ($)		Dec. 31, 2016 GBP (£)	Dec. 31, 2015 USD ($)	[1]	Dec. 31, 2015 GBP (£)	Oct. 21, 2016 t	Oct. 01, 2014 GBP (£)
Loss Contingencies [Line Items]
Loss contingency accrual								$ 92,000,000
Write-off of wildfire regulatory asset								351,000,000	$ 0	[1]		$ 0
Litigation Settlement, Percent of Arbitration Expenses			95.00%
Reserve for Aliso Canyon costs								84,000,000	53,000,000	[2]
San Diego Gas and Electric Company [Member]
Loss Contingencies [Line Items]
Loss contingency accrual								3,000,000
Write-off of wildfire regulatory asset								351,000,000	0	[1]		$ 0
Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Loss contingency accrual								88,000,000
Recoverable costs through insurance settlement								887,000,000
Reserve for Aliso Canyon costs								$ 84,000,000	$ 53,000,000	[2]
Loss from Catastrophes, 2007 Wildfire [Member] | San Diego Gas and Electric Company [Member]
Loss Contingencies [Line Items]
Number of Appeals Pending | appeal								1
Write-off of wildfire regulatory asset								$ 351,000,000
Write-off of wildfire regulatory asset net of tax								208,000,000
Lawsuit Against MHI [Member] | San Diego Gas and Electric Company [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Percent of Arbitration Expenses			95.00%
Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Loss contingency accrual								$ 83,000,000
Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Amount of Natural Gas Released | Bcf								4.62
Loss contingency accrual								$ 83,000,000
Recorded estimated costs								$ 913,000,000
Perecentage of recorded estimated costs allocated to temporary relocation program								60.00%
Recoverable costs through insurance settlement								$ 887,000,000
Reserve for Aliso Canyon costs								84,000,000
Insurance receivable for Aliso Canyon costs								418,000,000
Proceeds from Insurance Settlement, Operating Activities								$ 469,000,000
Loss Contingency, Period Of Required Climate Reductions				20 years
Loss Contingency, Period Of Required Regulatory Climate Reductions				100 years
Loss Contingency, Target Emissions Level | t				9,000,000
Loss Contingency, Total Actual Emissions, Floor | t															90,350
Loss Contingency, Total Actual Emissions, Ceiling | t															108,950
Loss Contingency, Mitigation Requirement | t															109,000
Storage Facility Maximum Capacity | Bcf								86
Aliso Canyon Facility As A Percentage of SoCalGas Total Storage Capacity		28.00%						63.00%
Storage Facility, Working Gas Target | Bcf		23.6
Storage Facility, Working Gas Minimum | Bcf		14.8
Net Book Value Of Aliso Canyon Natural Gas Storage Facility								$ 644,000,000
Construction in Work Progress Of Aliso Canyon Natural Gas Storage Facility								$ 252,000,000
Damages from Product Defects [Member] | Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Maximum Occupational Safety And Health Fines							$ 75,000
Penalty Assessments							233,500
Maximum Other Assessments							$ 5,000,000
Sempra Mexico Property Disputes [Member]
Loss Contingencies [Line Items]
Number of lawsuits								2
HMRC VAT Claim [Member] | Plaintiffs [Member]
Loss Contingencies [Line Items]
Damages sought | £														£ 80
HMRC VAT Claim [Member] | Parent Company [Member]
Loss Contingencies [Line Items]
VAT Tax Claim Paid Upon Appeal | £																£ 86
Subsequent Event [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit	373
Number Of Plaintiffs | plaintiff	45,000
Minimum [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Liability insurance coverage								$ 1,200,000,000
Loss Contingency, Environmental Mitigation Period				5 years
Storage Facility, Working Gas Target | Bcf		0
Maximum [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member] | Southern California Gas Company [Member]
Loss Contingencies [Line Items]
Liability insurance coverage								1,400,000,000
Loss Contingency, Environmental Mitigation Period				10 years
Storage Facility, Working Gas Target | Bcf		24.6
Consolidated Class Action Complaints [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit						2
Property Class Action [Member]
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit						1
Complaints Filed by Public Entities [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party					$ 8,500,000
Complaints Filed by Public Entities [Member] | Health Study [Member]
Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party					$ 1,000,000
R B S Sempra Commodities [Member]
Loss Contingencies [Line Items]
Damages sought | £											£ 160
Investment in RBS Sempra Commodities LLP								$ 67,000,000

[1] As adjusted for the retrospective adoption of ASU 2016-15 and ASU 2016-18, which we discuss in Note 2.

[2] Reflects reclassifications to conform to current year presentation, which we discuss in Note 1.