Property, Plant and Equipment - Summary of property, plant and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 26,346	$ 25,355
Less accumulated depreciation and amortization	(16,409)	(15,600)
Total property, plant and equipment	9,937	9,755
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	21	21
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	10,422	10,343
Less accumulated depreciation and amortization	(3,472)	(3,258)
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	15,826	14,934
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 77	$ 57