Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Property, plant and equipment
Less: Accumulated depreciation	$ (199,573)		$ (197,038)
Property, plant and equipment, net	83,268		82,111
Depreciation	3,172	$ 2,926
Land
Property, plant and equipment
Property, plant and equipment gross	2,330		2,330
Buildings and improvements
Property, plant and equipment
Property, plant and equipment gross	63,875		63,621
Machinery and equipment
Property, plant and equipment
Property, plant and equipment gross	$ 216,636		$ 213,198