Note 4 - Inventories (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventory Valuation Reserves, Ending Balance	$ 3,000	$ 3,500
Inventory Write-down	1,612	$ 4,419	$ 695
Nonsaleable Inventory [Member]
Inventory Write-down	800
HA Raw Materials [Member]
Inventory Write-down	1,300
HYAFF-based Products [Member]
Inventory Write-down	$ 1,200