Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 493,561	$ 480,400
Less accumulated depreciation	(340,466)	(327,645)
Net property	153,095	152,755
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,747	3,835
Building
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	111,025	110,534
Machinery and Equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	360,989	349,667
Construction in Progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 17,800	$ 16,364