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Note 2 - Basis of Presentation and Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands |  | 3 Months Ended | 9 Months Ended | 41 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 02, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Apr. 26, 2024 | Dec. 31, 2023 | Sep. 22, 2023 | Aug. 02, 2021
Investments, Nonaccrual, Interest Income |  | $ 200 | $ 0 | $ 200 | $ 0 |  |  |  |  |
Investment, Income Attributable to Non-cash Paid-in-Kind Interest, Percent |  | 1.50% | 13.50% | 2.80% | 7.10% |  |  |  |  |
Interest Income, Operating, Paid in Kind |  |  |  | $ 2,114 | $ 6,088 |  |  |  |  |
Investment, Nonaccrual, Income Not Received in Cash, Percent |  | 4.60% | 5.10% | 6.00% | 4.90% |  |  |  |  |
Debt Issuance Costs, Net |  | $ 7,900 |  | $ 7,900 |  | $ 7,900 |  | $ 5,800 |  |
Accumulated Amortization, Debt Issuance Costs |  | 6,700 |  | 6,700 |  | $ 6,700 |  | 5,200 |  |
Amortization of Debt Issuance Costs |  | $ 500 | $ 500 | $ 1,272 | $ 1,433 |  |  |  |  |
Federal Excise Tax, Percent |  | 4.00% |  | 4.00% |  | 4.00% |  |  |  |
Excise and Sales Taxes |  | $ 400 | $ 200 | $ 1,100 | 500 |  |  |  |  |
Unrecognized Tax Benefits, Ending Balance |  | $ 0 |  | $ 0 |  | $ 0 |  | 0 |  |
Open Tax Year |  |  |  | 2024 2023 2022 2021 |  |  |  |  |  |
Proceeds from Issuance of Common Stock |  |  |  | $ 47,527 | $ 65,031 |  |  |  |  |
Share Repurchase Program, Authorized, Amount |  |  |  |  |  |  | $ 5,000 |  |  |
Stock Repurchased During Period, Shares (in shares) |  | 0 | 0 | 0 | 0 | 167,465 |  |  |  |
Stock Repurchased During Period, Per Share (in dollars per share) |  |  |  |  |  | $ 11.22 |  |  |  |
Stock Repurchased During Period, Value |  |  |  |  |  | $ 1,900 |  |  |  |
The 2021 Equity Distribution Agreement [Member] |  |  |  |  |  |  |  |  |  |
Equity Sales Agreement, Maximum Value |  |  |  |  |  |  |  |  |  | $ 100,000
Equity Sales Agreement, Remaining Amount Available for Issuance |  |  |  |  |  |  |  |  | $ 0 |
The 2023 Equity Distribution Agreement [Member] |  |  |  |  |  |  |  |  |  |
Equity Sales Agreement, Maximum Value |  |  |  |  |  |  |  |  | $ 150,000 |
Equity Sales Agreement, Remaining Amount Available for Issuance |  | $ 98,200 |  | $ 98,200 |  | 98,200 |  |  |  |
Stock Issued During Period, Shares, New Issues (in shares) |  | 1,709,096 | 1,186,303 | 4,279,141 | 2,240,326 |  |  |  |  |
Proceeds from Issuance of Common Stock |  | $ 18,400 | $ 13,900 | $ 47,500 | $ 26,100 |  |  |  |  |
Payments of Stock Issuance Costs |  | 400 | 400 | 1,000 | 700 |  |  |  |  |
Public Offering [Member] |  |  |  |  |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues (in shares) | 3,250,000 |  |  |  |  |  |  |  |  |
Proceeds from Issuance of Common Stock | $ 12,500 |  |  |  |  |  |  |  |  |
Payments of Stock Issuance Costs | $ 38,900 |  |  |  |  |  |  |  |  |
Four Investments [Member] |  |  |  |  |  |  |  |  |  |
Investments, Cost, Nonaccrual Status |  | 51,400 |  | 51,400 |  | 51,400 |  | 72,500 |  |
Investments, Fair Value, Nonaccrual Status |  | $ 36,100 |  | 36,100 |  | $ 36,100 |  | $ 27,600 |  |
One Investment [Member] |  |  |  |  |  |  |  |  |  |
Interest Income, Operating, Paid in Kind |  |  |  | $ 1,000 |  |  |  |  |  |
Three Investments [Member] |  |  |  |  |  |  |  |  |  |
Interest Income, Operating, Paid in Kind |  |  | $ 3,700 |  | $ 5,800 |  |  |  |  |

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