Note 12 - Convertible Senior Notes - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Amortization of debt issuance costs			$ 434	$ 444
The 5% Convertible Senior Notes Due 2024 [Member]
Contractual interest expense	$ 1,006	$ 1,006	2,013	2,013
Amortization of debt issuance costs	206	205	410	414
Total interest cost	$ 1,212	$ 1,211	$ 2,423	$ 2,427
Effective interest rate	5.10%	5.10%	5.10%	5.10%