PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Property, plant and equipment [Abstract]
Property, plant and equipment, gross	$ 158,821		$ 157,304
Accumulated depreciation	(115,499)		(113,809)
Property, plant and equipment, net	43,322		43,495
Depreciation expense	3,200	$ 3,500
Land [Member]
Property, plant and equipment [Abstract]
Property, plant and equipment, gross	2,266		2,259
Buildings and Improvements [Member]
Property, plant and equipment [Abstract]
Property, plant and equipment, gross	31,362		30,761
Machinery and Equipment [Member]
Property, plant and equipment [Abstract]
Property, plant and equipment, gross	122,984		122,773
Construction in Progress [Member]
Property, plant and equipment [Abstract]
Property, plant and equipment, gross	$ 2,209		$ 1,511