Note 10 - Fair Value Measurement - Schedule of Carrying and Fair Value Amounts (Details) - USD ($) $ in Thousands		Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021
Reported Value Measurement [Member]
Third Amended and Restated Credit Agreement - term loan (2)	[1]	$ 0	$ 123,750	$ 127,500
Fourth Amended and Restated Credit Agreement - revolver (2)	[1]	50,000	0	0
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[2]	66,675	15,600	10,850
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[1],[3]	230,000	207,354	203,771
Estimate of Fair Value Measurement [Member]
Third Amended and Restated Credit Agreement - term loan (2)	[1]	0	124,598	128,639
Fourth Amended and Restated Credit Agreement - revolver (2)	[1]	50,056	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[2]	65,565	15,459	10,801
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[1],[3]	$ 253,000	$ 313,785	$ 333,500

[1] 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 Third Amended and Restated Credit Agreement and Fourth Amended and Restated 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, the Third Amended and Restated Credit Agreement and Fourth Amended and Restated Credit Agreement.

[2] All marketable securities as of June 30, 2022, December 31, 2021 and June 30, 2021 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.

[3] Excluded from the carrying value is debt discount of $22.6 million and $26.2 million as of December 31, 2021 and June 30, 2021, respectively, related to the 2.75% Convertible Notes (see Notes 2 and 15).