LEASES - Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 8	$ 7
Finance Lease, Interest Expense	4	4
Operating Lease, Right-of-Use Asset, Amortization	7	8
Operating Lease, Interest Expense	2	2
Lease, Cost, Total	$ 21	$ 21