Property, Plant and Equipment - Summary of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 28, 2015	Dec. 31, 2014
Property, plant and equipment
Accumulated depreciation	$ (189,756)	$ (184,898)
Net property, plant and equipment	70,166	71,414
Land
Property, plant and equipment
Property, plant and equipment gross	3,044	3,044
Buildings and improvements
Property, plant and equipment
Property, plant and equipment gross	68,371	67,269
Machinery and equipment
Property, plant and equipment
Property, plant and equipment gross	$ 188,507	$ 185,999