OTHER CONTINGENCIES AND COMMITMENTS (Other Commitments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Payments for other commitments	$ 45	$ 48	$ 43
Operating Leased Assets [Line Items]
Present value of fixed capacity payments, portion classified as current liabilities	533	556
Present value of fixed capacity payments, portion classified as noncurrent liabilities	1,208	1,730
Qualifying Facilities
Operating Leased Assets [Line Items]
Capitalized asset for fixed capacity payments for corresponding assets	7	9
Capitalized asset for fixed capacity payments, accumulated amortization	11	9
Present value of fixed capacity payments, portion classified as current liabilities	2	2
Present value of fixed capacity payments, portion classified as noncurrent liabilities	$ 5	$ 7
Minimum
Operating Leased Assets [Line Items]
Extension option for operating leases	1 year
Maximum
Operating Leased Assets [Line Items]
Extension option for operating leases	5 years