Note 12 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	December 31, 201 9		December 31, 201 8		December 31, 201 7
Cost of goods sold	$	260	$	358	$	324
Research and development		920		1,970		1,901
Selling, general and administrative		3,877		2,840		2,069
Total	$	5,057	$	5,168	$	4,294

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

				Weighted
	Number of			Average
	Restricted			Grant Date
	Stock Units			Fair Value
Restricted stock units outstanding, January 1, 2019		—		$	—
Granted		1,029,085			2.53
Vested		—			—
Forfeited		(40,440	)		2.54
Restricted stock units outstanding, December 31, 2019		988,645		$	2.53

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

	Number of Stock Options Outstanding			Weighted- Average Exercise Price	Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
							(in thousands)
December 31, 2018	11,422,705		$	3.64
Granted	2,058,128			2.53
Forfeited	(442,979	)		2.57
Expired	(277,413	)		5.31
Exercised	(111,702	)		2.41
December 31, 2019	12,648,739		$	3.47	6.5	$	197
Vested and exercisable options—December 31, 2019	8,583,475		$	3.90	5.6	$	90
Vested and expected to vest—December 31, 2019	12,648,739		$	3.47	6.5	$	197

Schedule of Share-based Compensation, Stock Options Outstanding and Exercisable Activity [Table Text Block]

			Options Outstanding						Options Vested and Exercisable
Exercise Prices			Number of Stock Options Outstanding		Weighted-Average Remaining Contractual Life (Years)		Weighted-Average Exercise Price per Share		Shares Subject to Stock Options		Weighted-Average Exercise Price per Share
$1.68	-	$2.56		4,469,976		7.7	$	2.24		2,308,859	$	2.21
$2.57	-	$3.92		5,946,276		6.5	$	3.13		4,081,817	$	3.23
$4.08	-	$6.60		1,627,987		4.2	$	5.58		1,588,299	$	5.61
$8.18	-	$10.55		604,500		4.0	$	10.29		604,500	$	10.29
				12,648,739		6.5	$	3.47		8,583,475	$	3.90

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

	Year Ended December 31,
	201 9			201 8			201 7
Expected term (in years)		6.0			5.9			5.7
Risk-free interest rate	1.5%	-	2.5%	2.5%	-	3.1%	1.82%	-	2.09%
Expected volatility		85%			83%			73%
Expected dividend rate		0%			0%			0%