Note 12 - Net Loss Per Share Available to Common Stockholders - Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Net loss	$ (4,606)	$ (9,112)	$ (41,244)
Weighted-average shares used to compute net loss per share available to common stockholders, basic and diluted (in shares)	5,945	5,736
Net loss per share available to common stockholders, basic and diluted (Note 12) (in dollars per share)	$ (0.77)	$ (1.59)