Note 12 - Convertible Senior Notes (Tables)

9 Months Ended

Sep. 30, 2021

Notes Tables

Convertible Debt [Table Text Block]

	September 30,			December 31,
	2021			2020
Principal	$	80,500		$	80,500
Unamortized debt issuance costs		(2,028	)		(2,646	)
Net carrying amount	$	78,472		$	77,854

Interest Income and Interest Expense Disclosure [Table Text Block]

	Three months ended September 30,						Nine months ended September 30,
	2021			2020			2021			2020
Contractual interest expense	$	1,006		$	1,006		$	3,018		$	3,018
Amortization of debt issuance costs		208			209			618			623
Total interest cost	$	1,214		$	1,215		$	3,636		$	3,641
Effective interest rate		5.1	%		5.1	%		5.1	%		5.1	%