Note 2 - Summary of Significant Accounting Policies - Inventory Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory reserves	$ 774
Inventory reserves	946	$ 774
Inventory Valuation Reserve [Member]
Inventory reserves	774	483	$ 394
Charge to costs and expenses	138	312	94
Other additions (deductions)	34	(21)	(5)
Inventory reserves	$ 946	$ 774	$ 483