Income Taxes - Deferred tax assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred Tax Assets:
Inventories	$ 316	$ 326
Accrued employees compensation and benefits costs	405	444
Postretirement obligation (accumulated other comprehensive income)	621	1,039
State Net operating loss and credit carryforwards	173	147
Bad debt reserve	29	28
Warranty reserve	122	107
Research and experimental expenses	615
Other		104
Total deferred tax assets	2,281	2,195
Valuation allowance	(173)	(147)
Net deferred tax assets	2,108	2,048
Deferred tax liabilities:
Prepaid expenses	(72)	(126)
Property, plant and equipment	(964)	(1,022)
Total deferred tax liabilities	(1,036)	(1,148)
Net deferred tax asset	$ 1,072	$ 900