EMPLOYEE BENEFIT PLANS (Components of Regulatory Assets and Accumulated Other Comprehensive Loss Not Recognized as Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Plan, Defined Benefit [Member]
Pension And Other Employee Benefit Plans [Line Items]
Net Loss	$ 117	$ 118
Prior Service Cost (Benefit)	3	4
Other Retiree Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Net Loss	6	11
Prior Service Cost (Benefit)	$ (1)	$ (2)