PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 288,705	$ 285,687
Less: accumulated depreciation	100,770	95,894
Property, plant and equipment, net	187,935	189,793
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,563	7,262
Building [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	64,647	63,224
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	205,101	201,341
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 12,394	$ 13,860