Note 9 - Commitments and Contingencies (Details Textual) - USD ($) $ in Millions	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Long-term Incentive Plan, Payments			$ 0.4
Deferred Compensation Liability, Current and Noncurrent, Total	$ 2.1		2.1
Supplemental Unemployment Benefits, Severance Benefits	0.1		0.1
Payments for Postemployment Benefits		$ 0.4
Employee and Severance Agreement, Maximum Aggregate Exposure	0.6		0.6
Employee Severance [Member]
Restructuring Charges, Total			0.8
Payments for Restructuring	0.1		$ 0.9
Minimum [Member]
Long-term Incentive Plan, Bonus Pool Percent			0.20%	1.00%
Maximum [Member]
Long-term Incentive Plan, Bonus Pool Percent			1.30%
Private Equity Funds [Member]
Guarantor Obligations, Current Carrying Value	$ 3.8		$ 3.8