PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Property, plant and equipment
Property, plant and equipment, gross	$ 185,608	$ 179,231
Accumulated depreciation	(128,416)	(122,270)
Property, plant and equipment, net	57,192	56,961
Land, buildings and improvements
Property, plant and equipment
Property, plant and equipment, gross	84,651	81,311
Machinery, equipment and fixtures
Property, plant and equipment
Property, plant and equipment, gross	77,541	75,177
Office furniture, equipment and vehicles
Property, plant and equipment
Property, plant and equipment, gross	23,204	22,471
Construction in progress
Property, plant and equipment
Property, plant and equipment, gross	$ 212	$ 272