Note 7 - Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

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

	Nine Months Ended September 30,
	2020			2019
Expected life (in years)		1.25			1.25
Volatility		34.25	%		42.45	%
Risk-free interest rate		1.43	%		2.24	%
Expected dividend		—			—
Weighted average fair value of purchase rights granted during the period	$	4.83		$	4.08

	Three Months Ended September 30,						Nine Months Ended September 30,
	2020			2019			2020			2019
Expected life (in years)		4.45			4.46			4.45			4.46
Volatility		43.92	%		39.93	%		40.90	%		42.61	%
Risk-free interest rate		0.23	%		1.40	%		0.60	%		1.99	%
Expected dividend		—			—			—			—
Weighted average fair value per share of options granted during the period	$	6.92		$	4.70		$	5.75		$	4.61

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Costs of revenues	$	790	$	745	$	2,582	$	2,404
Research and development		1,148		1,062		3,613		3,681
Selling, general and administrative		1,192		925		3,281		2,557
Stock-based compensation expenses	$	3,130	$	2,732	$	9,476	$	8,642

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

						Weighted
				Weighted		Average
				Average		Remaining		Aggregate
	Number of			Exercise		Contractual		Intrinsic
	Options			Price per		Term		Value
	(in thousands)			Share		(years)		(in thousands)
Outstanding, January 1, 2020		745		$	10.64
Granted (weighted average fair value of $5.75 per share)		24		$	16.72
Exercised		(177	)	$	10.33
Canceled		(43	)	$	10.69
Expired		(10	)	$	10.06
Outstanding, September 30, 2020		539		$	11.02		3.56	$	4,188
Vested and expected to vest, September 30, 2020		531		$	10.96		3.48	$	4,158
Exercisable, September 30, 2020		433		$	10.08		2.32	$	3,779

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

				Weighted
				Average Grant
	Shares			Date Fair Value
	(in thousands)			Per Share
Nonvested, January 1, 2020		1,887		$	12.30
Granted		864		$	21.28
Vested		(652	)	$	13.33
Forfeited		(101	)	$	12.61
Nonvested, September 30, 2020		1,998		$	15.83