Note 2 - Summary of Significant Accounting Policies - Change in Fair Value of Preferred Stock Warrant Liability (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Derivative [Member] | ||||
| Fair value, beginning of period | $ 496 | |||
| Change in value | (60) | (60) | ||
| Embedded derivative liability from the issuance of Notes | 496 | |||
| Fair value at end of period | 436 | 436 | ||
| Warrant [Member] | ||||
| Fair value, beginning of period | 234 | 42 | 140 | 42 |
| Change in value | 94 | |||
| Exchange of warrants upon Merger | (234) | (234) | ||
| Fair value at end of period | $ 42 | $ 42 | ||