Property, Plant and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment, net
Property, plant and equipment, gross	$ 292,446		$ 292,446		$ 282,688
Accumulated depreciation and amortization	(200,548)		(200,548)		(190,007)
Property, plant and equipment, net	91,898		91,898		92,681
Depreciation expense	6,200	$ 6,000	12,300	$ 12,100
Land
Property, Plant and Equipment, net
Property, plant and equipment, gross	2,799		2,799		2,724
Buildings and improvements
Property, Plant and Equipment, net
Property, plant and equipment, gross	25,363		$ 25,363		25,731
Buildings and improvements | Minimum
Property, Plant and Equipment, net
Useful Life (Years)			30 years
Buildings and improvements | Maximum
Property, Plant and Equipment, net
Useful Life (Years)			40 years
Office furniture and equipment
Property, Plant and Equipment, net
Property, plant and equipment, gross	20,626		$ 20,626		19,902
Office furniture and equipment | Minimum
Property, Plant and Equipment, net
Useful Life (Years)			5 years
Office furniture and equipment | Maximum
Property, Plant and Equipment, net
Useful Life (Years)			8 years
Machinery and equipment
Property, Plant and Equipment, net
Property, plant and equipment, gross	$ 243,658		$ 243,658		$ 234,331
Machinery and equipment | Minimum
Property, Plant and Equipment, net
Useful Life (Years)			5 years
Machinery and equipment | Maximum
Property, Plant and Equipment, net
Useful Life (Years)			7 years