Note 4 - Inventories (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Inventory Write-down			$ 3,000	$ 54,000
Cost of Goods Sold [Member]
Inventory Write-down	$ 0	$ 0	$ 1,000	$ 80,000