Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property, plant and equipment
Less: Accumulated depreciation	$ (191,960)	$ (189,472)
Property, plant and equipment, net	77,456	69,872
Land
Property, plant and equipment
Property, plant and equipment gross	2,401	2,401
Buildings and improvements
Property, plant and equipment
Property, plant and equipment gross	66,533	65,731
Machinery and equipment
Property, plant and equipment
Property, plant and equipment gross	$ 200,482	$ 191,212