Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total	$ 515,065	$ 486,170
Less accumulated depreciation	(358,051)	(337,492)
Property, plant, and equipment, net	157,014	148,678	$ 155,839
Land
Property, Plant and Equipment [Line Items]
Total	3,312	2,684
Buildings
Property, Plant and Equipment [Line Items]
Total	119,970	111,762
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total	379,747	361,010
Construction in progress
Property, Plant and Equipment [Line Items]
Total	$ 12,036	$ 10,714