Note 7 - Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

Notes Tables

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

	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2014		1,235,526		$	4.19		7.1	$	7,709
Granted		589,924		$	12.68
Exercised		(25,188	)
Outstanding at September 30, 2015		1,800,262		$	7.00		7.4	$	13,061
Exercisable at September 30, 2015		775,789		$	3.22		5.2	$	8,310
Vested or expected to vest at September 30, 2015 (1)		1,683,543		$	6.91		7.3	$	12,403