EMPLOYEE BENEFITS PLANS (Pension and Other Postretirement Benefit Amounts included in Consolidated Balance Sheet ) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Assets	$ 442	$ 465
Regulatory Liabilities	(541)	(573)
Pension Benefits
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Assets	150	135
Regulatory Liabilities	0	0
Accrued Employee Expenses	(1)	(2)
Pension and Other Postretirement Benefits	(91)	(77)
Accumulated Other Comprehensive Loss, SERP	14	10
Net Amount Recognized	72	66
Other Postretirement Benefits
Pension And Other Employee Benefit Plans [Line Items]
Regulatory Assets	16	0
Regulatory Liabilities	0	(1)
Accrued Employee Expenses	(3)	(2)
Pension and Other Postretirement Benefits	(72)	(56)
Accumulated Other Comprehensive Loss, SERP	0	0
Net Amount Recognized	$ (59)	$ (59)