Product and Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net sales	$ 3,118	$ 5,158	$ 5,172	$ 4,659	$ 4,727	$ 5,002	$ 6,011	$ 4,106	$ 18,107	$ 19,846	$ 30,998
Long-lived assets located in US, percent	98.00%				98.00%				98.00%	98.00%
United States
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net sales									$ 17,736	$ 19,446	29,840
International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net sales									371	400	1,158
Commercial
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net sales									8,662	15,217	14,809
Military maritime
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net sales									$ 9,445	$ 4,629	$ 16,189