Property, Plant and Equipment (Schedule of Plant Property and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 562,032	$ 537,785
Accumulated depreciation	(365,844)	(341,119)
Property, plant and equipment, net	196,188	196,666
Equipment in process	76,190	63,580
Total property, plant and equipment, net	272,378	260,246
Land and improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	22,589	21,697
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	155,669	165,968
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	324,773	281,771
Office equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 59,001	$ 68,349