Note 10 - Fair Value Measurement - Schedule of Carrying and Fair Value Amounts (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[1]	$ 36,728	$ 15,600	$ 11,300
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[2],[3]	230,000	207,354	202,018
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Term Loan [Member]
Notes		60,938	123,750	129,375
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[1]	35,909	15,459	11,258
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[2],[3]	276,288	313,785	324,013
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Term Loan [Member]
Notes		$ 62,861	$ 124,598	$ 130,645

[1] All marketable securities as of March 31, 2022, December 31, 2021 and March 31, 2021 were classified as held-to-maturity and consisted of U.S. Government and agency obligations and corporate commercial paper maturing in three months to five years.

[2] Excluded from the carrying value is debt discount of $22.6 million and $28.0 million as of December 31, 2021 and March 31, 2021, respectively, related to the 2.75% Convertible Notes (see Notes 2 and 15).

[3] The fair value of the 2.75% Convertible Notes is based on the median price of the notes in an active market. The fair value of 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 15 for more information about the 2.75% Convertible Notes and the Credit Agreement.