Note 10 - Significant Risk Concentrations - Rebate Credits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cost of Sales [Member]
Reductions	$ 26	$ 500	$ 236	$ 654
Selling and Marketing Expense [Member]
Reductions	$ 110	$ 123	$ 287	$ 1,026