Note 17 - Net Loss Per Share Attributable to Common Stockholders - Calculation of Basic and Diluted Net (Loss) Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Net loss	$ (6,409)	$ (5,260)	$ (5,637)	$ (1,339)	$ (4,902)	$ (6,548)	$ (8,871)	$ 2,314	$ (18,645)	$ (18,007)
Preferred dividend										(339)
Net loss attributable to common stockholders					$ (4,902)	$ (6,548)	$ (8,871)	$ 1,975	$ (18,645)	$ (18,346)
Shares used to compute net loss per share – basic and diluted (in shares)									21,569,523	6,316,065
Net loss per share – basic and diluted (in dollars per share)	$ (0.13)	$ (0.32)	$ (0.39)	$ (0.18)					$ (0.86)	$ (2.90)