Note 8 - Income Taxes (Details Textual) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	26.50%	22.70%
Unrecognized Tax Benefits, Ending Balance	$ 52.9
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	43.6
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 4.2