Note 6 - Convertible Senior Notes - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Total		$ 0	$ 1,672	$ 2,785	$ 2,243
March 2023 Note [Member] | Convertible Senior Notes [Member]
3% Convertible Notes Maturing April 1, 2028	[1]	391,882		391,882
Total		476,327		476,327
Contractual interest expense		3,010		3,341
Amortization of issuance costs		501		555
Total		$ 3,511		$ 3,896

[1] The carrying amounts presented are net of unamortized debt issuance costs of $10,618 as of June 30, 2023.