Note 4 - Management Actions (Details Textual) - USD ($) $ in Millions	3 Months Ended				9 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Dec. 31, 2020
Restructuring Charges, Total			$ 3.1	$ 2.0	$ 0.9	$ 6.2
Employee Severance [Member]
Restructuring Charges, Total			1.4	1.3
Other Restructuring [Member]
Restructuring Charges, Total			1.7	0.7
Selling, General and Administrative Expenses [Member]
Restructuring Charges, Total			1.9
Selling, General and Administrative Expenses [Member] | Employee Severance [Member]
Restructuring Charges, Total	$ 0.9	$ 3.5		1.7
Cost of Sales [Member]
Restructuring Charges, Total			$ 1.2
Inventory Write-down				1.7
Cost of Sales [Member] | Employee Severance [Member]
Restructuring Charges, Total				$ 0.3