Note 4 - Inventories (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Inventory Write-down			$ 52,000
Cost of Goods Sold [Member]
Inventory Write-down	$ 78,000	$ 12,000	$ 80,000	$ 15,000