INCOME TAXES - UNRECOGNIZED TAX BENEFITS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits
Beginning balance	$ 93	$ 119	$ 89
Increase in prior period tax positions	3	5	7
Decrease in prior period tax positions	(1)	0	(1)
Increase in current period tax positions	4	2	24
Settlements with taxing authorities	0	(32)	0
Expiration of statutes of limitations	0	(1)	0
Ending balance	99	93	119
Of the total, amounts related to tax positions that, if recognized, in future years, would decrease the effective tax rate	(87)	(81)	(107)
Of the total, amounts related to tax positions that, if recognized, in future years, would increase the effective tax rate	31	27	24
San Diego Gas and Electric Company [Member]
Reconciliation of Unrecognized Tax Benefits
Beginning balance	12	11	10
Increase in prior period tax positions	1	1	1
Ending balance	13	12	11
Of the total, amounts related to tax positions that, if recognized, in future years, would decrease the effective tax rate	(10)	(9)	(9)
Of the total, amounts related to tax positions that, if recognized, in future years, would increase the effective tax rate	1	1	1
Southern California Gas Company [Member]
Reconciliation of Unrecognized Tax Benefits
Beginning balance	64	61	35
Increase in prior period tax positions	1	1	2
Increase in current period tax positions	3	2	24
Ending balance	68	64	61
Of the total, amounts related to tax positions that, if recognized, in future years, would decrease the effective tax rate	(59)	(55)	(51)
Of the total, amounts related to tax positions that, if recognized, in future years, would increase the effective tax rate	$ 30	$ 26	$ 23