SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - ASSET RETIREMENT OBLIGATIONS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 2,553	$ 2,255
Accretion expense	109	101
Liabilities incurred and acquired	34	35
Deconsolidation and reclassification	0	(16)
Payments	(63)	(47)
Revisions	244	225
Ending Balance	2,877	2,553
Asset retirement obligations deconsolidated		12
Asset retirement obligations reclassified		4
San Diego Gas and Electric Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	830	828
Accretion expense	39	38
Liabilities incurred and acquired	17	0
Deconsolidation and reclassification	0	0
Payments	(61)	(46)
Revisions	14	10
Ending Balance	839	830
Southern California Gas Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	1,659	1,383
Accretion expense	66	61
Liabilities incurred and acquired	0	0
Deconsolidation and reclassification	0	0
Payments	(2)	0
Revisions	230	215
Ending Balance	$ 1,953	$ 1,659