Note 9 - Stockholders' Equity and Stock-based Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2018

Notes Tables

Share-based Compensation, Stock Options, Activity [Table Text Block]

			Options Outstanding
	Shares Available for Grant		Number of Stock Options Outstanding		Weighted- Average Exercise Price
Balance as of December 31, 2017		1,494,865		839,919	$	16.46
Options granted		(21,010)		21,010		50.65
Stock awards granted (1)		(530,876)
Options exercised		—		(241,021)		10.16
Options canceled		46,333		(46,333)		22.14
Stock awards canceled (1)		95,775		—		—
Balance, as of September 30, 2018		1,085,088		573,575	$	19.90

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

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
Cost of revenue	$	196	$	101	$	576	$	377
Sales and marketing
Employee		572		394		1,684		1,215
Non-Employee		(32)		—		60		—
Research and development		164		157		617		633
General and administrative		731		345		2,587		1,398
Total stock-based compensation expense	$	1,631	$	997	$	5,524	$	3,623