Select balance sheet data - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 290,975	$ 289,063
Less accumulated depreciation	169,279	164,000
Total property, plant and equipment, net	121,696	125,063
Land [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 1,264	1,264
Property, plant and equipment useful lives	Indefinite
Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 3,169	3,169
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	15 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	39 years
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 58,373	58,021
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	15 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	39 years
Machinery, Equipment and Tooling [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 205,813	204,248
Machinery, Equipment and Tooling [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	3 years
Machinery, Equipment and Tooling [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	10 years
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 3,718	3,738
Property, plant and equipment useful lives	5 years
Office Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 15,763	15,469
Office Furniture and Fixtures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	3 years
Office Furniture and Fixtures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful lives	7 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 2,875	$ 3,154