LEASES - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 20	$ 20
Financing cash flows for financing leases	13	16
ROU assets obtained in exchange for new (modified) lease liabilities:
Operating leases	3	6
Financing leases	$ 4	$ 5