PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Property, plant and equipment
Property, plant and equipment, gross	$ 76,920	$ 73,685
Less accumulated depreciation	(37,545)	(35,282)
Property, plant and equipment, net	39,375	38,403
Depreciation expense	1,907	1,657
Land
Property, plant and equipment
Property, plant and equipment, gross	1,000	993
Building and improvements
Property, plant and equipment
Property, plant and equipment, gross	10,967	10,678
Machinery, equipment, tools and dies
Property, plant and equipment
Property, plant and equipment, gross	51,367	49,083
Furniture, fixtures and other
Property, plant and equipment
Property, plant and equipment, gross	$ 13,586	$ 12,931