Note 9 - Fair Value Measurement - Schedule of Carrying and Fair Value Amounts (Details) - USD ($) $ in Thousands		Mar. 31, 2023	Dec. 31, 2022
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[1]	$ 56,329	$ 65,943
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[2]	230,000	230,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Credit Agreement - revolver (2)	[2]	50,000	50,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[1]	55,272	64,584
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[2]	311,880	281,365
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Credit Agreement - revolver (2)	[2]	$ 49,110	$ 49,536

[1] All marketable securities as of March 31, 2023 and December 31, 2022 were classified as held-to-maturity and consisted of U.S. Government and agency obligations and corporate commercial paper maturing in two months to three years.

[2] The fair value of our 2.75% convertible senior notes due 2024 (the "2.75% Convertible Notes") is based on the median price of the notes in an active market. The fair value of the Fourth Amended and Restated Credit Agreement (the "Credit Agreement") is based on borrowing rates available to us for long-term loans with similar terms, average maturities, and credit risk. See Note 14 for more information about the 2.75% Convertible Notes and the Credit Agreement. During the three months ended March 31, 2023 and 2022, we did not record any fair value adjustments related to nonfinancial assets and liabilities measured at fair value on a nonrecurring basis.