ACQUISTION AND DIVESTITURE ACTIVITY - ASSETS HELD FOR SALE (Details) - Sempra Mexico [Member] - Termoelectrica de Mexicali [Member] $ in Millions	1 Months Ended			3 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Feb. 29, 2016 MW	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Generating capacity (in mw) | MW			625
Other than temporary impairment in investment	$ 71	$ 131		$ 71	$ 131
Other than temporary impairment in investment, net of tax		$ 111			$ 111
Deferred tax expense						$ (8)	$ 8
Disposal Group Held-for-sale [Member]
Assets Held for Sale, Assets [Abstract]
Inventories						10
Other current assets						59
Property, plant and equipment, net						56
Other noncurrent assets						2
Total assets held for sale						127
Assets Held for Sale, Liabilities [Abstract]
Accounts payable						5
Other current liabilities						38
Asset retirement obligations						5
Other noncurrent liabilities						1
Total liabilities held for sale						$ 49