EMPLOYEE BENEFIT PLANS (Pension and Other Postretirement Benefit Amounts included in Consolidated Balance Sheet ) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Assets	$ 281	$ 264
Pension Plan [Member]
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Assets	123	115
Accrued Employee Expenses	(1)	(1)
Pension and Other Retiree Benefits	(69)	(57)
Accumulated Other Comprehensive Loss, SERP	6	5
Net Total Amount On Balance Sheet	59	62
Other Postretirement Benefits [Member]
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Assets	5	5
Accrued Employee Expenses	(2)	(2)
Pension and Other Retiree Benefits	(63)	(63)
Accumulated Other Comprehensive Loss, SERP	0	0
Net Total Amount On Balance Sheet	$ (60)	$ (60)