Note 6 - Equity Incentive Plan (Tables)

3 Months Ended

Mar. 31, 2018

Notes Tables

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

	Three Months Ended March 31,
	2018					2017
Risk free interest rate		2.15%	-	2	.37%		1.70%	-	1.78%
Expected volatility		38.74%	-	40.81%			43.47%	-	44.30%
Expected life (years)			4.5					4.0
Expected dividend yield			0.00%					0.00%

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended March 31,
	2018			2017
Cost of product revenue	$	(216	)	$	97
Research & development		210			10
Selling, general & administrative		7,571			1,075
Total stock-based compensation expense	$	7,565		$	1,182