Note 8 - Fair Value Measurement - Schedule of Carrying and Fair Value Amounts (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[1]	$ 5,200	$ 32,799
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Term Loan [Member]
Notes	[2]	131,250	138,750
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[2],[3]	200,303	193,696
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Credit Agreement - revolving credit facility	[2]	0	25,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Held-to-maturity marketable securities (1)	[1]	5,200	32,792
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Term Loan [Member]
Notes	[2]	133,030	139,042
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
2.75% Convertible Notes	[2],[3]	248,400	249,895
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Revolving Credit Facility [Member]
Credit Agreement - revolving credit facility	[2]	$ 0	$ 25,043

[1] All marketable securities were classified as held-to-maturity and consisted of U.S. Government and agency obligations as of December 31, 2020 and 2019.

[2] The fair values of the 2019 Notes, Credit Agreement term loan and revolving credit facility are based on borrowing rates available to us for long-term loans with similar terms, average maturities, and credit risk. The fair value of the 2.75% Convertible Notes is based on the median price of the notes in an active market as of December 31, 2020 and 2019. See Note 14 for definitions of, and more information about the Credit Agreement and 2.75% Convertible Notes.

[3] Excluded from carrying value is $29.7 million and $36.3 million debt discount as of December 31, 2020 and 2019, respectively, related to the 2.75% Convertible Notes (see Note 14).