Note 5 - Preferred Stock (Details Textual) - USD ($) | | | | 3 Months Ended | 6 Months Ended | 12 Months Ended | 18 Months Ended | |
Oct. 06, 2023 | Mar. 31, 2023 | Mar. 31, 2023 | Mar. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2024 | Jun. 30, 2023 | Dec. 31, 2023 | Jun. 30, 2024 | Dec. 31, 2022 |
Preferred Stock, Shares Authorized (in shares) | | | | | 42,000 | 42,000 | | 42,000 | 42,000 | |
Preferred Stock, Shares Designated (in shares) | | | | | 1,983,250 | 1,983,250 | | | 1,983,250 | |
Preferred Stock, Shares Issued (in shares) | | | | | 545 | 545 | | 1,930 | 545 | |
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | | | | | $ 0.0001 | $ 0.0001 | | $ 0.0001 | $ 0.0001 | |
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ 0.2792 | | | | | | | | | |
Preferred Stock, Shares Outstanding (in shares) | | | | | 545 | 545 | | 1,930 | 545 | |
Class of Warrant or Right, Outstanding (in shares) | | | | | 5,101,345 | 5,101,345 | | | 5,101,345 | |
Conversion of Series F Preferred Stock to Common Stock [Member] | | | | | | | | | | |
Conversion of Stock, Shares Converted (in shares) | | | | | 2,111 | 3,033 | | | | |
Conversion of Stock, Shares Issued (in shares) | | | | | 7,955,743 | 11,558,000 | | 14,102,000 | 25,660,000 | |
Preferred Warrants [Member] | | | | | | | | | | |
Class of Warrant or Right, Exercised (in shares) | | | | | 1,648 | 1,648 | | | | |
Proceeds from Warrant Exercises | | | | | | $ 1,478,000 | $ 0 | | | |
Class of Warrant or Right, Cash Fee, Percentage of Proceeds | | | | | 8% | | | | | |
Class of Warrant or Right, Cash Fee | | | | | $ 129,000 | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | | | $ 975 | $ 975 | | | $ 975 | |
Warrants and Rights Outstanding, Term (Year) | | | | | 3 years | 3 years | | | 3 years | |
Class of Warrant or Right, Percentage of Securities Called by Warrants or Rights | | | | | 100% | 100% | | | 100% | |
Class of Warrant or Right, Outstanding (in shares) | | | | | 31,102 | 31,102 | | | 31,102 | |
Common Warrants [Member] | | | | | | | | | | |
Class of Warrant or Right, Exercised (in shares) | | | | | | | | 746,027 | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | | | $ 1.71 | $ 1.71 | | $ 1.73 | $ 1.71 | $ 0 |
Class of Warrant or Right, Issued (in shares) | | | | | 963,745 | 963,745 | | 4,543,626 | | |
Class of Warrant or Right, Outstanding (in shares) | | | | | 5,101,345 | 5,101,345 | | 4,137,850 | 5,101,345 | 343,099 |
Private Placement [Member] | | | | | | | | | | |
Proceeds from Issuance or Sale of Equity | | | $ 6,386,000 | | | | | | | |
Proceeds from Issuance or Sale of Equity, Net | | | 5,364,000 | | | | | | | |
Payments of Stock Issuance Costs | | | $ 1,022,000 | | | | | | | |
Private Placement [Member] | Preferred Warrants [Member] | | | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | | | | 32,750 | | | | | | |
Private Placement [Member] | Investor Warrants [Member] | | | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | | | | 3,830,417 | | | | | | |
Series F Preferred Stock [Member] | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | | 6,550 | | | | 1,648 | | | | |
Preferred Stock, Convertible, Conversion Price (in dollars per share) | | | | $ 1.71 | $ 0.33 | $ 0.33 | $ 1.71 | | $ 0.33 | |
Preferred Stock, Convertible, Conversion Price Percentage | | | | 80% | | | | | | |
Preferred Stock, Stated Value Per Share (in dollars per share) | $ 1,000 | | | | | | | | | |
Preferred Stock, Dividend Rate, Percentage | 9% | | | | | 20% | | | | |
Conversion of Stock, Shares Converted (in shares) | | | | | | 3,033 | | 4,620 | | |
Preferred Stock, Shares Outstanding (in shares) | | | | | 545 | 545 | | 1,930 | 545 | |
Dividends Payable | | | | | $ 4,000,000 | $ 4,000,000 | | $ 136,000,000 | $ 4,000,000 | |
Stock Issued During Period, Shares, Warrants Exercised (in shares) | | | | | 1,648 | 1,648 | | | | |
Proceeds from Warrant Exercises | | | | | $ 1,607,000 | $ 1,607,000 | | | | |
Proceeds From Warrant Exercises, Net | | | | | $ 1,478,000 | $ 1,478,000 | | | | |
Series F Preferred Stock [Member] | Private Placement [Member] | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | | | | 6,550 | | | | | | |
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | | | | $ 0.0001 | | | | | | |
Maximum [Member] | | | | | | | | | | |
Preferred Stock, Shares Authorized (in shares) | | | | | 5,000,000 | 5,000,000 | | | 5,000,000 | |