Note 9 - Stock Options and Restricted Stock - Potentially Dilutive Instruments (Details) - shares |
3 Months Ended | |
|---|---|---|
Mar. 31, 2022 |
Mar. 31, 2021 |
|
| Potentially dilutive instruments (in shares) | 1,374,640 | 1,300,463 |
| Share-Based Payment Arrangement, Option [Member] | ||
| Potentially dilutive instruments (in shares) | 1,334 | 6,235 |
| Restricted Stock [Member] | ||
| Potentially dilutive instruments (in shares) | 181,221 | 170,338 |
| Warrant [Member] | ||
| Potentially dilutive instruments (in shares) | 1,192,085 | 1,123,890 |