PROPERTY, PLANT AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property, plant and equipment
Property, plant and equipment, gross	$ 184,437	$ 183,786
Accumulated depreciation	(119,062)	(117,912)
Property, plant and equipment, net	65,375	65,874
Land, buildings and improvements
Property, plant and equipment
Property, plant and equipment, gross	84,139	83,119
Machinery, equipment and fixtures
Property, plant and equipment
Property, plant and equipment, gross	77,675	78,003
Office furniture, equipment and vehicles
Property, plant and equipment
Property, plant and equipment, gross	22,164	22,265
Construction in progress
Property, plant and equipment
Property, plant and equipment, gross	$ 459	$ 399