EMPLOYEE BENEFIT PLANS (Changes in Regulatory Assets and Accumulated Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits | Regulatory Asset
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current Year Actuarial (Gain) Loss	$ 5	$ 15	$ 5
Amortization of Net Loss	(7)	(7)	(7)
Total Recognized (Gain) Loss	(2)	8	(2)
Pension Benefits | Accumulated Other Comprehensive Loss
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current Year Actuarial (Gain) Loss	3	1	0
Amortization of Net Loss	0	0	0
Total Recognized (Gain) Loss	3	1	0
Other Postretirement Benefits | Regulatory Asset
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current Year Actuarial (Gain) Loss	(1)	0	(4)
Amortization of Net Loss	0	0	0
Total Recognized (Gain) Loss	$ (1)	$ 0	$ (4)