Note 11 - Stockholders' Equity (Details Textual) - USD ($)
$ / shares in Units, $ in Thousands |
|
12 Months Ended |
Jun. 02, 2020 |
Dec. 31, 2021 |
Dec. 31, 2020 |
| Common Stock, Shares Authorized (in shares) |
|
150,000,000
|
150,000,000
|
| Common Stock, Par or Stated Value Per Share (in dollars per share) |
|
$ 0.0001
|
$ 0.0001
|
| Preferred Stock, Shares Authorized (in shares) |
|
5,000,000
|
5,000,000
|
| Preferred Stock, Par or Stated Value Per Share (in dollars per share) |
|
$ 0.0001
|
$ 0.0001
|
| Proceeds from issuance of Common Stock and Warrants |
|
$ 0
|
$ 12,400
|
| Proceeds from Warrant Exercises |
|
$ 12,047
|
$ 26,191
|
| Class of Warrant or Right, Exercised During Period (in shares) |
|
1,815,012,000
|
5,155,976
|
| Payments of Facilitating Exercise of Warrants |
|
|
$ 1,017
|
| Proceeds from Warrant Exercises, Net of Exercise Costs |
|
|
25,174
|
| Officer [Member] |
|
|
|
| Proceeds from Warrant Exercises |
|
|
$ 1,667
|
| Class of Warrant or Right, Exercised During Period (in shares) |
|
|
333,334
|
| Class of Warrant or Right, Exercised During Period, Exercise Price (in dollars per share) |
|
|
$ 5.00
|
| Warrants Issued with June 2019 Follow-On Offering [Member] |
|
|
|
| Warrants and Rights Outstanding, Term (Year) |
2 years
|
|
|
| Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) |
$ 6.00
|
|
|
| June 2020 Follow-on Public Offering [Member] |
|
|
|
| Number of Shares Per Unit Issued (in shares) |
1
|
|
|
| Number of Warrants Per Unit (in shares) |
1
|
|
|
| Shares Issued, Price Per Share (in dollars per share) |
$ 6.00
|
|
|
| Equity Offering, Units Issued (in shares) |
2,066,667
|
|
|
| Proceeds from issuance of Common Stock and Warrants |
$ 12,400
|
|
|
| Proceeds From Issuance of Common Stock and Warrants, Net of Issuance Costs |
$ 11,670
|
|
|