Note 15 - Net Loss Per Share - Basic and Diluted Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net loss	$ (12,308)	$ (10,310)	$ (6,697)
Weighted-average shares used in computing net loss per share, basic and diluted (in shares)	38,160,543	8,368,284	1,560,293
Net loss per share, basic and diluted (in dollars per share)	$ (0.32)	$ (1.23)	$ (4.29)