Note 3 - Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares |
12 Months Ended | |
---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
Antidilutive securities (in shares) | 1,468,105 | 717,431 |
Employee and Non-employee Stock Options [Member] | ||
Antidilutive securities (in shares) | 639,359 | 480,035 |
Common Stock Purchase Warrants [Member] | ||
Antidilutive securities (in shares) | 807,563 | 216,213 |
Deferred Share Units [Member] | ||
Antidilutive securities (in shares) | 21,183 | 21,183 |