Note 9 - Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	Stock Plans						Employee Stock Purchase Plan
	2019			2018			2019			2018
Expected life (in years)		4.46			4.43			1.25			1.25
Volatility		41.56	%		43.91	%		44.85	%		42.85	%
Risk-free interest rate		1.86	%		2.73	%		2.49	%		2.48	%
Expected dividend		—			—			—			—

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

	Year Ended December 31,
	2019		2018
Costs of revenues	$	3,185	$	3,554
Research and development		4,764		3,260
Selling, general and administrative		3,474		3,481
Stock-based compensation expenses	$	11,423	$	10,295

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

	Outstanding Options
	Number of Options (in thousands)			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding, January 1, 2018		1,045		$	9.65
Granted (weighted average fair value of $4.08 per share)		116		$	10.35
Exercised		(81	)	$	6.93
Canceled		(30	)	$	13.41
Expired		(23	)	$	13.16
Outstanding, December 31, 2018		1,027		$	9.75
Granted (weighted average fair value of $5.00 per share)		102		$	13.79
Exercised		(238	)	$	5.41
Canceled		(87	)	$	14.57
Expired		(59	)	$	15.83
Outstanding, December 31, 2019		745		$	10.64		4.49	$	4,777
Vested and expected to vest, December 31, 2019		731		$	10.59		4.40	$	4,722
Exercisable, December 31, 2019		571		$	9.92		3.21	$	4,090

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

	Shares (in thousands)			Fair Value
Nonvested, January 1, 2018		1,617		$	15.66
Granted		983		$	8.66
Vested		(596	)	$	15.84
Forfeited		(169	)	$	14.83
Nonvested, December 31, 2018		1,835		$	11.93
Granted		952		$	13.52
Vested		(710	)	$	13.05
Forfeited		(190	)	$	12.18
Nonvested, December 31, 2019		1,887		$	12.30