Income Taxes - Deferred tax assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Assets:
Inventories	$ 473	$ 417
Accrued employees compensation and benefits costs	446	478
Accrued arbitration award and related liability	324	234
Net operating loss and credit carryforwards	236	248
Bad debt reserve	71	37
Warranty reserve.	88	90
Total deferred tax assets	1,638	1,504
Valuation allowance	(236)	(248)
Net deferred tax asset	1,402	1,256
Deferred tax liabilities:
Prepaid expenses	(32)	(28)
Property, plant and equipment	(1,238)	(910)
Other		(14)
Minimum pension liability	(25)	(9)
Total deferred tax liabilities	(1,295)	(961)
Net deferred tax asset	$ 107	$ 295