Note 4 - Employee Benefit Plans (Details Textual) - USD ($) $ in Millions	1 Months Ended				3 Months Ended		9 Months Ended
	Oct. 31, 2022	May 31, 2022	Sep. 30, 2021	Jan. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 4.2	$ 5.6	$ 5.4	$ 16.8
Nonoperating Income (Expense) [Member]
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component					$ 1.4	$ 0.2	$ 4.1	$ 0.5