EMPLOYEE BENEFIT PLANS (Components of Regulatory Assets and Accumulated Other Comprehensive Loss Not Recognized as Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Pension Plan [Member]
Pension And Other Employee Benefit Plans [Line Items]
Net Loss	$ 128	$ 117
Prior Service Cost (Benefit)	0	3
Other Postretirement Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Net Loss	6	6
Prior Service Cost (Benefit)	$ (1)	$ (1)