LEASES - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating lease right-of-use ("ROU") assets, included in Other assets	$ 40	$ 43
Current operating lease liabilities, included in Accrued expenses and other current liabilities	7	6
Noncurrent operating lease liabilities, included in Other liabilities	40	43
Total operating lease liabilities	47	49
Property and equipment, at cost	170	170
Accumulated amortization	(37)	(33)
Property and equipment, net	133	137
Total finance lease liabilities	82	85
Project Debt, Current
Lessee, Lease, Description [Line Items]
Current obligations of finance leases, included in Current portion of long-term debt	6	6
Project Debt, Noncurrent
Lessee, Lease, Description [Line Items]
Finance leases, net of current obligations, included in Long-term debt	69	72
Long Term Debt, Excluding Current Maturities
Lessee, Lease, Description [Line Items]
Finance leases, net of current obligations, included in Long-term debt	6	6
Long Term Debt, Current Maturities
Lessee, Lease, Description [Line Items]
Current obligations of finance leases, included in Current portion of long-term debt	$ 1	$ 1