SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - CAPITALIZED FINANCING COSTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Capitalized Financing Costs Disclosure [Line Items]
Total capitalized financing costs	$ 256	$ 236	$ 201
San Diego Gas and Electric Company [Member]
Capitalized Financing Costs Disclosure [Line Items]
Total capitalized financing costs	85	62	51
Southern California Gas Company [Member]
Capitalized Financing Costs Disclosure [Line Items]
Total capitalized financing costs	$ 60	$ 55	$ 49