SIGNIFICANT ACCOUNTING POLICIES AND OTHER FINANCIAL DATA - ASSET RETIREMENT OBLIGATIONS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 3,083	$ 2,972
Accretion expense	127	123
Liabilities incurred	2	2
Deconsolidation	0	(2)
Payments	(63)	(46)
Revisions	140	34
Ending Balance	3,289	3,083
San Diego Gas and Electric Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	866	874
Accretion expense	39	39
Liabilities incurred	0	0
Deconsolidation	0	(2)
Payments	(60)	(44)
Revisions	31	(1)
Ending Balance	876	866
Southern California Gas Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	2,177	2,063
Accretion expense	86	81
Liabilities incurred	0	0
Deconsolidation	0	0
Payments	(2)	(2)
Revisions	107	35
Ending Balance	$ 2,368	$ 2,177