Note 2 - Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Retained Earnings (Accumulated Deficit)	$ (65,963)	$ (60,142)
Cash and Cash Equivalents, at Carrying Value	15,109	21,352	$ 1,687	$ 3,557
Short-term Investments	$ 1,796