Income Taxes - Deferred tax assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred Tax Assets:
Inventories	$ 326	$ 455
Accrued employees compensation and benefits costs	444	397
Postretirement obligation (accumulated other comprehensive income)	1,039	360
Warranty reserve	107	80
Operating loss carryforward	147	147
Bad debt reserve	28	40
Other	104	67
Total deferred tax assets	2,195	1,546
Valuation allowance	(147)	(147)
Net deferred tax asset	2,048	1,399
Deferred tax liabilities:
Prepaid expenses	(126)	(62)
Property, plant and equipment	(1,022)	(1,200)
Total deferred tax liabilities	(1,148)	(1,262)
Net deferred tax asset	$ 900	$ 137