Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Summary of property, plant and equipment
Land	$ 1,000	$ 1,000
Building	3,361	3,361
Machinery and equipment	10,636	10,530
Furniture and fixtures	440	437
Office equipment	2,401	2,439
Building improvements	1,458	1,433
Property, plant and equipment, gross	19,296	19,200
Less: Accumulated depreciation and amortization	(16,406)	(16,094)
Property, plant and equipment, Net	$ 2,890	$ 3,106