Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Leases	$ 233	$ 319
Employee benefits	1,208	1,471
Accrued losses on uncompleted contracts	2,572	3,015
Stock based compensation expense	247	225
Federal net operating losses	21,724	19,345
State net operating losses	3,299	3,620
R&D and other tax credits	938	806
Other	545	398
Total deferred tax assets	30,766	29,199
Deferred tax liabilities
Property, plant and equipment and AHFS	(1,285)	(2,632)
Prepaid insurance	(231)	(511)
Total deferred tax liabilities	(1,516)	(3,143)
Net deferred tax assets	29,250	26,056
Valuation allowance	(29,331)	(26,168)
Net deferred taxes	$ (81)	$ (112)