EMPLOYEE BENEFITS PLANS (Changes in Regulatory Assets and Accumulated Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits | Regulatory Asset
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current Year Actuarial (Gain) Loss	$ 23	$ 16	$ 12
Amortization of Net Loss	(8)	(8)	(7)
Prior Service (Credit) Cost	0	0	0
Total Recognized (Gain) Loss	15	8	5
Pension Benefits | AOCI
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current Year Actuarial (Gain) Loss	5	4	(1)
Amortization of Net Loss	(1)	(1)	0
Prior Service (Credit) Cost	0	1	(1)
Total Recognized (Gain) Loss	4	4	(2)
Other Postretirement Benefits | Regulatory Asset
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current Year Actuarial (Gain) Loss	17	1	(6)
Amortization of Net Loss	0	0	0
Prior Service (Credit) Cost	0	0	(2)
Total Recognized (Gain) Loss	$ 17	$ 1	$ (8)