Note 8 - Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	23.30%	23.90%	24.90%	23.90%
Unrecognized Tax Benefits, Ending Balance	$ 55.2		$ 55.2
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	45.4		45.4
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 5.5		$ 5.5