Note 11 - Common Stock and Stock-based Compensation Plans (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of options and SAR units (1)			Weighted average exercise price		Weighted average remaining contractual term		Aggregate intrinsic- value
Outstanding as of December 31, 2018		702,817		$	19.88		4.3	$	2,708
Granted		—			—
Exercised		(54,114	)		16.73
Forfeited or expired		(730	)		21.83
Outstanding as of September 30, 2019 (2)		647,973		$	20.14		3.7	$	6,361
Exercisable as of September 30, 2019 (3)		611,677		$	19.62		3.6	$	6,313

Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]

	Number of RSUs and PSUs			Weighted Average Grant-Date Fair Value
Unvested as of December 31, 2018		564,390		$	32.28
Granted		489,099			27.77
Vested		(266,820	)		29.78
Forfeited or expired		(49,117	)		31.19
Unvested as of September 30, 2019		737,552		$	30.27

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Nine months ended September 30,				Three months ended September 30,
	2019 (unaudited)		2018 (unaudited)		2019 (unaudited)		2018 (unaudited)
Cost of revenue	$	464	$	480	$	168	$	155
Research and development, net		4,314		3,874		1,494		1,246
Sales and marketing		1,112		1,246		362		369
General and administrative		1,957		2,483		728		697
Total equity-based compensation expense	$	7,847	$	8,083	$	2,752	$	2,467

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]

	Nine months ended September 30,						Three months ended September 30,
	2019 (unaudited)			2018 (unaudited)			2019 (unaudited)			2018 (unaudited)
Expected dividend yield		0%			0%			0	%		0	%
Expected volatility	42%	-	43%	35%	-	42%		42	%		38	%
Risk-free interest rate	2.0%	-	2.5%	0.7%	-	2.2%		2.0	%		2.2	%
Contractual term of up to (months)		24			24			24			24