PROPERTY, PLANT AND EQUIPMENT - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total	$ 464,804		$ 464,804		$ 457,045
Accumulated depreciation and amortization	(300,112)		(300,112)		(286,736)
Property, plant and equipment, net	164,692		164,692		170,309
Assets under finance leases	6,100		6,100		4,800
Accumulated amortization for assets under finance leases	1,200		1,200		900
Depreciation expense	6,800	$ 7,800	14,300	$ 15,900
Land
Property, Plant and Equipment [Line Items]
Total	5,796		5,796		5,805
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Total	58,113		58,113		57,632
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total	306,557		306,557		302,886
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	11,791		11,791		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	21,076		21,076		20,508
Automobiles
Property, Plant and Equipment [Line Items]
Total	4,396		4,396		4,518
Construction in progress
Property, Plant and Equipment [Line Items]
Total	$ 11,158		$ 11,158		$ 8,329