Note 7 - Income Taxes (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Income Taxes Receivable	$ 33.7	$ 3.1
Unrecognized Tax Benefits, Ending Balance	78.5	66.1	$ 50.6	$ 52.2
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	67.2	57.1
Income Tax Examination, Penalties and Interest Accrued, Total	3.5	2.9	$ 3.2
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued, Total	$ 6.4	$ 5.6
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Open Tax Year	2018 2019 2020 2021
State and Local Jurisdiction [Member]
Open Tax Year	2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021