Note 1 - General (Details Textual) - Trade Accounts Receivable [Member] - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 18,100	$ 18,100	$ 13,300
Accounts Receivable, Credit Loss Expense (Reversal)	0	5,300
Accounts Receivable, Allowance for Credit Loss, Writeoff	$ 0	$ 500