Note 11 - Capitalization and Equity Structure (Details Textual) - USD ($) $ / shares in Units, $ in Thousands | | | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | | | | |
Sep. 03, 2024 | Jan. 10, 2024 | Sep. 30, 2024 | Feb. 28, 2021 | Oct. 31, 2020 | Jun. 30, 2020 | Sep. 30, 2024 | Jun. 30, 2024 | Mar. 31, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023 | Dec. 31, 2019 | Jun. 30, 2019 | May 31, 2019 |
Common Stock, Shares Authorized (in shares) | | | 141,429,000 | | | | 141,429,000 | | | | | 141,429,000 | | 141,429,000 | | | |
Preferred Stock, Shares Authorized (in shares) | | | 10,000,000 | | | | 10,000,000 | | | | | 10,000,000 | | 10,000,000 | | | |
Common Stock, Shares, Outstanding (in shares) | | | 21,998,000 | | | | 21,998,000 | | | | | 21,998,000 | | 14,848,000 | | | |
Preferred Stock, Shares Outstanding (in shares) | | | 0 | | | | 0 | | | | | 0 | | 0 | | | |
Proceeds from Issuance of Common Stock | | | | | | | | | | | | $ 9,021 | $ 0 | | | | |
Stock Issued During Period, Value, New Issues | | | | | | | | $ 47 | $ 3,970 | | | | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 14,900,000 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 15,612,000 | | | | 15,612,000 | | | | | 15,612,000 | | 1,240,000 | | | |
Common Stock, Shares, Issued (in shares) | | | 21,998,000 | | | | 21,998,000 | | | | | 21,998,000 | | 14,848,000 | | | |
Preferred Stock, Shares Issued (in shares) | | | 0 | | | | 0 | | | | | 0 | | 0 | | | |
September 2024 Pre-funded Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | 2,900 | | 2,900 | | | | 2,900 | | | | | 2,900 | | | | | |
Shares Issued, Price Per Share (in dollars per share) | | | $ 1 | | | | $ 1 | | | | | $ 1 | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 0.001 | | | | $ 0.001 | | | | | $ 0.001 | | | | | |
Proceeds from Issuance of Warrants | | | $ 2,897 | | | | | | | | | | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 2,900 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 2,565 | | | | 2,565 | | | | | 2,565 | | 0 | | | |
September 2024 Series A Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | 6,000 | | 6,000 | | | | 6,000 | | | | | 6,000 | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 1 | | | | $ 1 | | | | | $ 1 | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 6,000 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 6,000 | | | | 6,000 | | | | | 6,000 | | 0 | | | |
Warrants and Rights Outstanding, Term (Year) | | | 4 years 10 months 24 days | | | | 4 years 10 months 24 days | | | | | 4 years 10 months 24 days | | | | | |
September 2024 Series B Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | 6,000 | | 6,000 | | | | 6,000 | | | | | 6,000 | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 1 | | | | $ 1 | | | | | $ 1 | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 6,000 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 6,000 | | | | 6,000 | | | | | 6,000 | | 0 | | | |
Warrants and Rights Outstanding, Term (Year) | | | 10 months 24 days | | | | 10 months 24 days | | | | | 10 months 24 days | | | | | |
September 2024 Warrants [Member] | | | | | | | | | | | | | | | | | |
Beneficial Ownership Limitation, Percentage | | | 4.99% | | | | | | | | | | | | | | |
Beneficial Ownership Limitation, Contingency, Percentage Increase Available for Grant | | | 9.99% | | | | | | | | | | | | | | |
A2021 Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 12.81 | $ 12.81 | | | $ 12.81 | | | | | $ 12.81 | | | | | |
Beneficial Ownership Limitation, Contingency, Percentage Increase Available for Grant | | | | | | | | | | | | 9.99% | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | 273,000 | | | | | | | | 0 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 273,000 | | | | 273,000 | | | | | 273,000 | | 273,000 | | | |
Warrants and Rights Outstanding, Term (Year) | | | 1 year 4 months 24 days | | | | 1 year 4 months 24 days | | | | | 1 year 4 months 24 days | | | | | |
June 2020 Investor Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 5.18 | | | $ 5.18 | $ 5.18 | | | | | $ 5.18 | | | | | |
Beneficial Ownership Limitation, Contingency, Percentage Increase Available for Grant | | | | | | | | | | | | 9.99% | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 0 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 127,000 | | | 874,000 | 127,000 | | | | | 127,000 | | 127,000 | | | |
Warrants and Rights Outstanding, Term (Year) | | | 1 year 2 months 12 days | | | | 1 year 2 months 12 days | | | | | 1 year 2 months 12 days | | | | | |
June 2020 Placement Agent Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 5.64 | | | $ 5.64 | $ 5.64 | | | | | $ 5.64 | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | 122,000 | | | | | | 0 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 39,000 | | | | 39,000 | | | | | 39,000 | | 39,000 | | | |
Warrants and Rights Outstanding, Term (Year) | | | 8 months 12 days | | | | 8 months 12 days | | | | | 8 months 12 days | | | | | |
December 2019 Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 8.1 | | | | $ 8.1 | | | | | $ 8.1 | | | | $ 8.1 | |
Beneficial Ownership Limitation, Contingency, Percentage Increase Available for Grant | | | | | | | | | | | | 9.99% | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 0 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 556,000 | | | | 556,000 | | | | | 556,000 | | 556,000 | | 556,000 | |
Warrants and Rights Outstanding, Term (Year) | | | 8 months 12 days | | | | 8 months 12 days | | | | | 8 months 12 days | | | | | |
December 2019 Placement Agent Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 8.44 | | | | $ 8.44 | | | | | $ 8.44 | | | $ 8.44 | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 0 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 52,000 | | | | 52,000 | | | | | 52,000 | | 52,000 | 52,000 | | |
Warrants and Rights Outstanding, Term (Year) | | | 2 months 12 days | | | | 2 months 12 days | | | | | 2 months 12 days | | | | | |
May 2019 Warrants [Member] | | | | | | | | | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | $ 1.55 | | | | $ 1.55 | | | | | $ 1.55 | | | | | |
Class Of Warrant Or Right Issued (in shares) | | | | | | | | | | | | 0 | | | | | |
Class of Warrant or Right, Outstanding (in shares) | | | 0 | | | | 0 | | | | | 0 | | 193,000 | | | 444,000 |
Warrants and Rights Outstanding, Term (Year) | | | | | | | | | | | | | | | | | 5 years |
September 2024 Offering [Member] | | | | | | | | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | 3,100 | | | | | | | | | | | | | | | | |
Proceeds from Issuance or Sale of Equity | $ 5,004 | | | | | | | | | | | | | | | | |
Stock Issued During Period, Value, New Issues | | | | | | | $ 5,004 | | | | | | | | | | |
January 2024 Offering [Member] | | | | | | | | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | | 2,968,000 | | | | | | | | | | | | | | | |
Shares Issued, Price Per Share (in dollars per share) | | $ 1.55 | | | | | | | | | | | | | | | |
Proceeds from Issuance of Common Stock | | $ 3,932 | | | | | | | | | | | | | | | |
At the Market Offering [Member] | | | | | | | | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | | | | | | | 0 | | | 0 | 105,000 | | | | | | |
Proceeds from Issuance of Common Stock | | | | | | | | | | | $ 85 | | | | | | |
Stock Issued During Period, Value, New Issues | | | | | $ 5,000 | | | | | | | | | | | | |
Shares Issued, Average Price Per Share (in dollars per share) | | | | | | | | | | | $ 1.43 | | | | | | |
Sale Of Stock, Stock Available For Issuance, Value | | | | | | | | | | | $ 4,134 | | | | | | |
At the Market Offering [Member] | Minimum [Member] | | | | | | | | | | | | | | | | | |
Share Price (in dollars per share) | | | | | $ 6.75 | | | | | | | | | | | | |