LEASES - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
LEASES
Operating lease costs	$ 1,908	$ 2,052	$ 3,842	$ 4,218
Finance lease costs:
Amortization of assets	2,782	4,784	6,796	9,507
Interest on lease liabilities	639	763	1,309	1,553
Total finance lease costs	3,421	5,547	8,105	11,060
Variable and short-term lease costs	703	284	1,286	411
Total lease costs	$ 6,032	$ 7,883	$ 13,233	$ 15,689