Note 2 - Investments and Fair Value Measurement - Summary of Changes in Fair Value of Level III Financial Liabilities (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2020 |
Sep. 30, 2019 |
Sep. 30, 2020 |
Sep. 30, 2019 |
|
| Fair value, Beginning of period | $ 591 | $ 657 | $ 437 | $ 121 |
| Fair value of contingent put option associated with the Loan Agreement | (85) | (143) | 69 | 514 |
| Change in fair value of contingent put option associated with the Prior Agreement | 0 | (121) | ||
| Fair value, End of period | $ 506 | $ 514 | $ 506 | $ 514 |