Note 8 - Employee Benefit Plans (Details Textual) - USD ($) $ in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Jul. 31, 2018	Apr. 30, 2018	Sep. 30, 2018	Sep. 30, 2018
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 1.2	$ 1.3		$ 5.5
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year			$ 0.5	0.5
Other Nonoperating Income (Expense) [Member]
Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component			$ 0.7	$ 2.1