COMMITMENTS AND CONTINGENCIES - OTHER LITIGATION (Details) £ in Millions, $ in Millions	Oct. 21, 2016 t	Sep. 30, 2016 USD ($)	Oct. 01, 2015 GBP (£)	Sep. 01, 2012 GBP (£)
HMRC VAT Claim [Member]
Loss Contingencies [Line Items]
VAT tax claim paid upon appeal | £			£ 146	£ 86
Investment in RBS Sempra commodities LLP | $		$ 67
Southern California Gas Company [Member] | Subsequent Event [Member] | Aliso Canyon Natural Gas Storage Facility Gas Leak [Member]
Loss Contingencies [Line Items]
Loss Contingency, Total Actual Emissions, Floor	90,350
Loss Contingency, Total Actual Emissions, Ceiling	108,950