PROPERTY, PLANT AND EQUIPMENT - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total	$ 438,190		$ 438,190		$ 416,611
Accumulated depreciation and amortization	(245,426)		(245,426)		(221,817)
Property, plant and equipment, net	192,764		192,764		194,794
Assets under finance leases, net of accumulated amortization	5,226		5,226		5,200
Depreciation expense	8,400	$ 8,900	25,700	$ 27,100
Land
Property, Plant and Equipment [Line Items]
Total	6,360		6,360		6,376
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Total	58,375		58,375		57,006
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total	277,692		277,692		269,084
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	10,703		10,703		10,253
Capitalized Enterprise Resource Planning system development costs
Property, Plant and Equipment [Line Items]
Total	46,637		46,637		46,637
Computers and computer software
Property, Plant and Equipment [Line Items]
Total	22,008		22,008		15,826
Automobiles
Property, Plant and Equipment [Line Items]
Total	4,638		4,638		4,879
Construction in progress
Property, Plant and Equipment [Line Items]
Total	$ 11,777		$ 11,777		$ 6,550