Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 853,497	$ 835,341
Less accumulated depreciation	(482,966)	(476,043)
Property, plant and equipment, net	370,531	359,298
Depreciation expense	48,914	48,693	$ 43,165
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	23,239	21,723
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	183,544	182,226
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 646,714	$ 631,392