Note 10 - Stock Incentive Plans - Share-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Total compensation cost for share-based payments	$ 642	$ 261	$ 1,209	$ 842
Weighted average grant-date fair value of equity instruments granted (per share) (in dollars per share)	$ 0.80	$ 2.27	$ 0.97	$ 2.26
Total fair value of shares vested during the period		$ 83	$ 1,524	$ 2,369
Unamortized share-based payments			$ 2,039	$ 2,276
Weighted average period to be recognized as expense (Year)			1 year 73 days	1 year 255 days