Note 2 - Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Retained Earnings (Accumulated Deficit), Total	$ (147,529)	$ (140,604)
Cash and Cash Equivalents, at Carrying Value, Total	$ 4,305	$ 7,363
Cash, Percentage Held in One Financial Institution	99.00%
Cash, Uninsured Amount	$ 4,000