PROPERTY, PLANT AND EQUIPMENT - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total	$ 464,858		$ 464,858		$ 457,045
Accumulated depreciation	(303,989)		(303,989)		(286,736)
Property, plant and equipment, net	160,869		160,869		170,309
Assets under finance leases	6,700		6,700		5,700
Accumulated amortization for assets under finance leases	1,400		1,400		900
Depreciation expense	6,700	$ 7,900	21,000	$ 23,800
Land
Property, Plant and Equipment [Line Items]
Total	5,755		5,755		5,805
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Total	57,779		57,779		57,632
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total	304,803		304,803		302,886
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	11,666		11,666		11,450
Capitalized ERP system development costs
Property, Plant and Equipment [Line Items]
Total	45,917		45,917		45,917
Computers and computer software
Property, Plant and Equipment [Line Items]
Total	21,781		21,781		20,508
Automobiles
Property, Plant and Equipment [Line Items]
Total	4,327		4,327		4,518
Construction in progress
Property, Plant and Equipment [Line Items]
Total	$ 12,830		$ 12,830		$ 8,329