Note 8 - Inventories (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Inventory Write-down			$ 7.4
Reserve Estimate, Change [Member]
Inventory Write-down	$ 0.5	$ 3.0
Systems [Member]
Inventory Write-down			$ 1.5