Note 11 - Net Loss Per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Year Ended December 31,
	2016		2015		2014
Convertible preferred stock		-		-		7,581,475	(a)
Common stock warrants		-		-		659,806	(a)
Outstanding stock options		2,166,254		2,200,369		1,235,526
Convertible notes		-		-		243,876	(a)
		2,166,254		2,200,369		9,720,683