Note 5 - Inventories (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Inventory Valuation Reserves, Ending Balance	$ 6,900	$ 3,000
Inventory Write-down	5,490	$ 1,612	$ 4,419
Nonsaleable Inventory [Member]
Inventory Write-down	$ 2,800