Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment
Property, Plant and Equipment	$ 300,906	$ 294,910
Accumulated Depreciation	(217,430)	(208,717)
Property, Plant and Equipment, Net	83,476	86,193
Depreciation expense	17,686	18,072	18,088
Land
Property, Plant and Equipment
Property, Plant and Equipment	4,311	4,294
Buildings and improvements
Property, Plant and Equipment
Property, Plant and Equipment	53,490	52,597
Machinery and manufacturing equipment
Property, Plant and Equipment
Property, Plant and Equipment	143,413	140,330
Office equipment
Property, Plant and Equipment
Property, Plant and Equipment	91,048	88,814
Work in progress
Property, Plant and Equipment
Property, Plant and Equipment	$ 8,644	$ 8,875