EMPLOYEE BENEFIT PLANS - NARRATIVE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Dedicated assets in support of certain benefit plans	$ 455	$ 430	[1]
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in plan liability due to divestiture	0	61
Change in plan assets due to divestiture	0	44
Increase in liability due to special termination benefits	0	0
Settlements	194	75
Settlement charge	38	16
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Change in plan liability due to divestiture	0	6
Change in plan assets due to divestiture	0	4
Increase in liability due to special termination benefits	18	26
Settlements	0	1
San Diego Gas and Electric Company [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase in liability due to special termination benefits	0	0
Settlements	0	75
Settlement charge	0	16		$ 0
San Diego Gas and Electric Company [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase in liability due to special termination benefits	0	14
Settlements	0	0
Settlement charge	0	0		0
Southern California Gas Company [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase in liability due to special termination benefits	0	0
Settlements	175	0
Settlement charge	30	0		0
Southern California Gas Company [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase in liability due to special termination benefits	18	11
Settlements	0	0
Settlement charge	$ 0	$ 0		$ 0

[1] Reflects reclassifications to conform to current year presentation, which we discuss in Note 1.