5. Income Taxes (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax liabilities (assets):
Property, plant and equipment	$ 6,787	$ 9,550
Patents and goodwill	1,740	2,833
Benefit plans	(854)	(1,819)
Inventories	(282)	(519)
Capital loss carryover	(572)	(954)
Other	(116)	(338)
Deferred tax liabilities (assets)	6,703	8,753
Plus: Valuation allowance	609	0
Total deferred tax liabilities	$ 7,312	$ 8,753