LEASES - Components of Lease Expense and Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
LEASES
Operating lease cost	$ 16,409	$ 15,194
Short-term lease cost	2,712	3,426
Variable lease cost	4,059	2,803
Total operating lease cost	23,180	21,423
Payments for lease liabilities	16,100	15,100
Lease liabilities arising from ROU	7,800	9,700
Finance lease cost:
Amortization of right-of-use asset	2,181	2,318
Variable costs	852	964
Total finance lease cost	3,033	3,282
Finance leases cost included in property, plant and equipment	25,400	25,900
Accumulated amortization related to finance leases	$ 9,500	$ 9,400
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet	us-gaap:PropertyPlantAndEquipmentNet
Principal payments, finance lease liabilities	$ 400
Additional finance lease liabilities recognized	1,600
Finance lease liability	1,200
Finance lease liability, current	$ 300