Note 12 - Convertible Senior Notes (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

Convertible Debt [Table Text Block]

	September 30,			December 31,
	2020			2019
Principal	$	80,500		$	80,500
Unamortized debt issuance costs		(2,854	)		(3,459	)
Net carrying amount	$	77,646		$	77,041

Interest Income and Interest Expense Disclosure [Table Text Block]

	Three months ended September 30,						Nine months ended September 30,
	2020			2019			2020			2019
Contractual interest expense	$	1,006		$	984		$	3,018		$	2,270
Amortization of debt issuance costs		209			207			623			473
Total interest cost	$	1,215		$	1,191		$	3,641		$	2,743
Effective interest rate		5.1	%		5.1	%		5.1	%		5.1	%