Note 4 - Inventories (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventory Write-down	$ 1,000
Cost of Goods Sold [Member]
Inventory Write-down	$ 36,000	$ 12,000	$ 33,000