Note 11 - Income Taxes - Deferred Income Tax Assets (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Foreign tax credits	$ 3,000	$ 66,000
Inventory reserve	101,000	107,000
Accrued expenses and inventory	334,000	311,000
Current deferred income tax assets, net	438,000	484,000
Non-current deferred income taxes:
Property and equipment	(683,000)	(681,000)
Intangible assets	(4,000)	(3,000)
Marketable securities	112,000	78,000
Basis diffence in investments	(129,000)	(129,000)
Foreign exchange	(12,000)	(45,000)
Other	(20,000)	(12,000)
State income taxes	(71,000)	(75,000)
Non-current deferred income tax liabilities	(807,000)	(867,000)
Net deferred income tax liability	$ (369,000)	$ (383,000)