Income Taxes - Deferred tax assets (liabilities) (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Inventories	$ 417	$ 406
Accrued employees compensation and benefits costs	478	430
Accrued arbitration award and related liability	234	268
Net operating loss and credit carryforwards	248	269
Bad debt reserve	37	33
Warranty reserve	90	8
Other	0	33
Minimum pension liability	0	9
Total deferred tax assets	1,504	1,456
Valuation allowance	(248)	(279)
Net deferred tax asset	1,256	1,177
Deferred tax liabilities:
Prepaid expenses	(28)	0
Property, plant and equipment	(910)	(768)
Other	(14)	0
Minimum pension liability	(9)	0
Total deferred tax liabilities	(961)	(768)
Net deferred tax asset	$ 295	$ 409