Note 11 - Accounts Receivable Securitization (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument, Fee Amount	$ 1,156	$ 1,441	$ 2,593
Line of Credit [Member] | Accounts Receivable Securitization Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 100,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.60%
Accounts Receivable Eligible for Securitization	$ 31,868	41,282
Line of Credit Facility, Fair Value of Amount Outstanding	0	0
Letters of Credit Outstanding, Amount	31,218	41,211
Line of Credit Facility, Remaining Borrowing Capacity	$ 650	$ 71
Line of Credit [Member] | Accounts Receivable Securitization Facility [Member] | Minimum [Member]
Line of Credit Facility, Commitment Fee Percentage	2.00%
Line of Credit [Member] | Accounts Receivable Securitization Facility [Member] | Maximum [Member]
Line of Credit Facility, Commitment Fee Percentage	2.50%