INCOME TAXES - CHANGES IN UNRECOGNIZED TAX BENEFITS (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	$ (8)	$ (38)	$ (34)
San Diego Gas and Electric Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	(6)	(11)	(9)
Expiration of statutes of limitations on tax assessments [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	0	(2)	(2)
Expiration of statutes of limitations on tax assessments [Member] | San Diego Gas and Electric Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	0	(1)	(1)
Potential resolution of audit issues with various U.S. federal, state, and local non-U.S. taxing authorities [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	(8)	(36)	(32)
Potential resolution of audit issues with various U.S. federal, state, and local non-U.S. taxing authorities [Member] | San Diego Gas and Electric Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	(6)	(10)	(8)
Potential resolution of audit issues with various U.S. federal, state, and local non-U.S. taxing authorities [Member] | Southern California Gas Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Possible change in unrecognized tax benefits in next 12 months	$ (2)	$ (25)	$ (22)