Note 4 - Restricted Cash and Restricted Cash Equivalents - Receivable Bond (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Bond proceeds	$ 68,995	$ 0	$ 0
Total restricted cash	95,200
Total restricted cash and restricted cash equivalents	95,200
Current portion	(25,032)	0	0
Long-term restricted cash and restricted cash equivalents	70,168	$ 0	$ 0
Receivable from Bond Trustee [Member]
Total restricted cash	24,010
Cash Pledged and Assigned to Citibank, N.A. [Member]
Total restricted cash	71,190
The 2021 Bonds [Member]
Bond proceeds	68,995
Disbursement of funds	(44,780)
Interest paid on bonds	(216)
Interest income	$ 11