DERIVATIVE FINANCIAL INSTRUMENTS - DERIVATIVE COMMODITY VOLUMES (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2018 MWh MMBTU	Dec. 31, 2017 MWh MMBTU
Natural gas [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes | MMBTU	38	46
Electricity [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	2	3
Congestion revenue rights [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	49	59
SDG&E [Member] | Natural gas [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes | MMBTU	35	39
SDG&E [Member] | Electricity [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	2	3
SDG&E [Member] | Congestion revenue rights [Member]
Derivatives, Fair Value [Line Items]
Net derivative energy volumes	49	59