Note 2 - Summary of Significant Accounting Policies - Antidilutive Securities Excluded From Computation of Earnings Per Share (Details) - shares |
3 Months Ended | |||
|---|---|---|---|---|
Mar. 31, 2021 |
Mar. 31, 2020 |
|||
| Total potential dilutive securities (in shares) | [1] | 5,818,431 | 4,912,152 | |
| Share-based Payment Arrangement, Option [Member] | ||||
| Total potential dilutive securities (in shares) | [1] | 1,040,522 | 1,709,106 | |
| Restricted Stock Units (RSUs) [Member] | ||||
| Total potential dilutive securities (in shares) | 4,771,537 | 2,397,299 | ||
| Warrant [Member] | ||||
| Total potential dilutive securities (in shares) | [1] | 6,372 | 805,747 | |
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