Note 7 - Employee Benefit Plans (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Plan, Cost	$ 32.5	$ 28.1	$ 24.5
Deferred Compensation Liability, Current and Noncurrent, Total	25.1	26.0
Other Current Assets [Member] | Defined Benefit Plan, Equity Securities [Member]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	$ 25.1	$ 26.0