Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 487,278	$ 480,400
Less accumulated depreciation	(334,074)	(327,645)
Net property	153,204	152,755
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,795	3,835
Building
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	111,436	110,534
Machinery and Equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	351,647	349,667
Construction in Progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 20,400	$ 16,364