DERIVATIVE FINANCIAL INSTRUMENTS - DERIVATIVE COMMODITY VOLUMES (Details) MWh in Millions, MMBTU in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018 MWh MMBTU	Dec. 31, 2017 MWh MMBTU
SDG&E [Member] | Natural gas [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	33	39
SDG&E [Member] | Electricity [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes | MWh	3	3
SDG&E [Member] | Congestion revenue rights [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes | MWh	57	59
Sempra LNG & Midstream [Member] | Natural gas [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	5	3
Sempra Mexico [Member] | Natural gas [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	17	4