Property, Plant and Equipment - Summary of property, plant and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 32,710	$ 32,050
Less accumulated depreciation and amortization	(20,693)	(19,333)
Total property, plant and equipment	12,017	12,717
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	7	7
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	11,359	11,017
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	21,146	20,695
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 198	$ 331