LEASES - Components of Lease Expense and Payments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
LEASES
Operating lease cost	$ 4,152	$ 3,627	$ 12,228	$ 11,294
Short-term lease cost	769	652	2,040	2,232
Variable lease cost	692	1,151	3,034	2,400
Total operating lease cost	5,613	5,430	17,302	15,926
Payments for lease liabilities			9,100	10,200
Lease liabilities arising from right-of-use assets			5,700	7,300
Finance lease cost:
Amortization of right-of-use asset	534	570	1,628	1,749
Variable costs	198	244	655	802
Total finance lease cost	732	$ 814	2,283	$ 2,551
Finance leases cost included in property, plant and equipment	$ 25,200		$ 25,200		$ 25,900
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentGross		us-gaap:PropertyPlantAndEquipmentGross		us-gaap:PropertyPlantAndEquipmentGross
Principal payments, finance lease liabilities			$ 600
Finance Lease Liabilities Recognized			1,500
Finance lease liability	$ 1,300		1,300
Finance Lease, Liability, Current	300		300
Accumulated depreciation related to finance leases	$ 9,000		$ 9,000		$ 9,400