Property, Plant and Equipment (Schedule of Plant Property and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 517,991	$ 444,365
Accumulated depreciation	(317,414)	(289,909)
Property, plant and equipment, net	200,577	154,456
Equipment in process	42,182	25,155
Total property, plant and equipment, net	242,759	179,611
Land
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	21,525	14,620
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	175,279	135,191
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	256,301	238,000
Office equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 64,886	$ 56,554