INCOME TAXES - UNRECOGNIZED TAX BENEFITS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits
Beginning balance	$ 90	$ 87	$ 117
Increase in prior period tax positions	22	2	10
Decrease in prior period tax positions	(15)	(2)	0
Increase in current period tax positions	4	6	8
Settlements with taxing authorities	(12)	(3)	(48)
Ending balance	89	90	87
Of the total, amounts related to tax positions that, if recognized, in future years, would decrease the effective tax rate	(77)	(87)	(83)
Of the total, amounts related to tax positions that, if recognized, in future years, would increase the effective tax rate	20	36	32
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Accrued interest and penalties	0	1	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense [Abstract]
Interest income and penalties on unrecognized income tax benefits	0	0	2
San Diego Gas and Electric Company [Member]
Reconciliation of Unrecognized Tax Benefits
Beginning balance	22	20	14
Increase in prior period tax positions	9	0	5
Decrease in prior period tax positions	(11)	0	0
Increase in current period tax positions	0	2	2
Settlements with taxing authorities	(10)	0	(1)
Ending balance	10	22	20
Of the total, amounts related to tax positions that, if recognized, in future years, would decrease the effective tax rate	(7)	(19)	(16)
Of the total, amounts related to tax positions that, if recognized, in future years, would increase the effective tax rate	1	13	11
Southern California Gas Company [Member]
Reconciliation of Unrecognized Tax Benefits
Beginning balance	29	27	19
Increase in prior period tax positions	3	0	2
Decrease in prior period tax positions	0	(2)	0
Increase in current period tax positions	4	4	6
Settlements with taxing authorities	(1)	0	0
Ending balance	35	29	27
Of the total, amounts related to tax positions that, if recognized, in future years, would decrease the effective tax rate	(26)	(29)	(27)
Of the total, amounts related to tax positions that, if recognized, in future years, would increase the effective tax rate	$ 20	$ 24	$ 21