Property, Plant and Equipment (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 663,393	$ 657,840
Accumulated depreciation	(457,497)	(450,161)
Property, plant and equipment, net	205,896	207,679
Land and land improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	8,537	8,537
Building and building improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	82,998	82,440
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	547,660	546,425
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	9,591	9,553
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 14,607	$ 10,885