Property, Plant and Equipment, net (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment, net.
Original cost of fully depreciated assets still in use	$ 131,300,000	$ 122,600,000
Depreciation expense	19,000,000	16,300,000	16,800,000
Property, Plant and Equipment
Property, plant and equipment, gross	425,224,000	394,705,000
Accumulated depreciation and amortization	(217,868,000)	(201,540,000)
Property, plant and equipment excluding capital projects in progress, net	207,356,000	193,165,000
Capital projects in progress	6,096,000	2,551,000
Property, plant and equipment, net	213,452,000	195,716,000
Impairment charges recorded for facility classified as an asset held for sale	803,000	1,094,000	419,000
Hungen, German facility
Property, Plant and Equipment
Impairment charges recorded for facility classified as an asset held for sale	300,000
Land
Property, Plant and Equipment
Property, plant and equipment, gross	32,068,000	28,996,000
Buildings and site improvements
Property, Plant and Equipment
Property, plant and equipment, gross	174,187,000	153,597,000
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	4,747,000	3,820,000
Machinery and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	$ 214,222,000	$ 208,292,000