Income Taxes - Deferred tax assets (liabilities) (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Inventories	$ 406	$ 604
Accrued employees compensation and benefits costs	430	696
Accrued arbitration award and related liability	268	160
Net operating loss and credit carryforwards	269	244
Bad debt reserve	33	26
Other	41	23
Minimum pension liability	9	10
Total deferred tax assets	1,456	1,763
Valuation allowance	(279)	(253)
Net deferred tax asset	1,177	1,510
Deferred tax liabilities:
Property, plant and equipment	(768)	(1,019)
Total deferred tax liabilities	(768)	(1,019)
Net deferred tax asset	$ 409	$ 491