Note 12 - Convertible Senior Notes (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

Convertible Debt [Table Text Block]

	June 30,			December 31,
	2021			2020
Principal	$	80,500		$	80,500
Unamortized debt issuance costs		(2,236	)		(2,646	)
Net carrying amount	$	78,264		$	77,854

Interest Income and Interest Expense Disclosure [Table Text Block]

	Three months ended June 30,						Six months ended June 30,
	2021			2020			2021			2020
Contractual interest expense	$	1,006		$	1,006		$	2,013		$	2,013
Amortization of debt issuance costs		206			205			410			414
Total interest cost	$	1,212		$	1,211		$	2,423		$	2,427
Effective interest rate		5.1	%		5.1	%		5.1	%		5.1	%