Note 5 - Inventories (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventory Write-down			$ 597,000
Cost of Goods Sold [Member]
Inventory Write-down	$ 12,000	$ 33,000	$ 52,000