Property, Plant and Equipment - Summary of property, plant and equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 26,256	$ 26,346
Less accumulated depreciation and amortization	(16,536)	(16,409)
Total property, plant and equipment	9,720	9,937
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	7	21
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	10,167	10,422
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	15,959	15,826
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 123	$ 77