Note 2 - Summary of Significant Accounting Policies - Change in Fair Value of Preferred Stock Warrant Liability (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Warrant [Member] | ||||
| Fair value, beginning of period | $ 42 | $ 140 | $ 42 | |
| Change in value | 1 | 94 | 1 | |
| Exchange of warrants upon Merger | (234) | |||
| Fair value at end of period | 43 | 43 | ||
| Derivative [Member] | ||||
| Fair value, beginning of period | 436 | |||
| Change in value | (152) | (211) | ||
| Embedded derivative liability from the issuance of Notes | 369 | 864 | ||
| Fair value at end of period | $ 653 | $ 653 | ||