DERIVATIVE FINANCIAL INSTRUMENTS - DERIVATIVE NOTIONALS (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Cross currency swaps [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivative	$ 306	$ 408
Cross currency swaps [Member] | Minimum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2018	Dec. 31, 2018
Cross currency swaps [Member] | Maximum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2023	Dec. 31, 2023
Other foreign currency derivatives [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivative	$ 975	$ 345
Other foreign currency derivatives [Member] | Minimum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2018	Dec. 31, 2018
Other foreign currency derivatives [Member] | Maximum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2019	Dec. 31, 2019
Cash Flow Hedging [Member] | Interest rate instruments [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivative	$ 845	$ 861
Cash Flow Hedging [Member] | Interest rate instruments [Member] | Minimum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2018	Dec. 31, 2018
Cash Flow Hedging [Member] | Interest rate instruments [Member] | Maximum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2032	Dec. 31, 2032
San Diego Gas and Electric Company [Member] | Cash Flow Hedging [Member] | Interest rate instruments [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivative	$ 292	$ 295
San Diego Gas and Electric Company [Member] | Cash Flow Hedging [Member] | Interest rate instruments [Member] | Minimum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2018	Dec. 31, 2018
San Diego Gas and Electric Company [Member] | Cash Flow Hedging [Member] | Interest rate instruments [Member] | Maximum [Member]
Derivatives, Fair Value [Line Items]
Maturity date	Dec. 31, 2019	Dec. 31, 2019