Note 6 - Convertible Senior Notes (Tables)

6 Months Ended

Jun. 30, 2023

Notes Tables

Schedule of Long-Term Debt Instruments [Table Text Block]

	As of June 30, 2023
	Carrying Value (1)		Fair Value
3% Convertible Notes Maturing April 1, 2028		391,882		476,327
Total		391,882		476,327

	Three Months Ended		Six Months Ended
	June 30, 2023
Contractual interest expense		3,010		3,341
Amortization of issuance costs		501		555
Total		3,511		3,896