Note 1 - General (Details Textual) - Trade Accounts Receivable [Member] - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 18.0	$ 18.0	$ 13.3
Accounts Receivable, Credit Loss Expense (Reversal)	4.7	6.2
Accounts Receivable, Allowance for Credit Loss, Writeoff	$ 1.1	$ 1.5