Financial Highlights - Summary of Financial Highlights (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Sep. 30, 2025 |
Sep. 30, 2024 |
Sep. 30, 2023 |
Sep. 30, 2022 |
Sep. 30, 2021 |
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| Investment Company, Financial Highlights [Abstract] | |||||||||||||||||||||
| Net Asset Value Per Share, Beginning Balance | $ 7.56 | $ 7.7 | $ 8.98 | $ 9.85 | $ 7.84 | ||||||||||||||||
| Net investment income | [1] | 0.71 | 0.92 | 1 | 0.66 | 0.54 | |||||||||||||||
| Net realized and unrealized (loss) gain | [1] | (0.21) | (0.17) | (1.52) | (1.03) | 1.94 | |||||||||||||||
| Net (decrease) increase in net assets resulting from operations | [1] | 0.5 | 0.75 | (0.52) | (0.37) | 2.48 | |||||||||||||||
| Distribution of net investment income | [1],[2] | (0.96) | (0.88) | (0.76) | (0.56) | (0.48) | |||||||||||||||
| Distribution of realized gains | [1],[2] | 0 | 0 | 0 | 0 | 0 | |||||||||||||||
| Total distributions to stockholders | (0.96) | (0.88) | (0.76) | (0.56) | (0.48) | ||||||||||||||||
| (Dilutive) effect of common stock issuance | 0 | (0.01) | 0 | 0 | 0 | ||||||||||||||||
| Repurchase of common stock | [1] | 0 | 0 | 0 | 0.06 | 0 | |||||||||||||||
| Net Asset Value Per Share, Ending Balance | 7.11 | 7.56 | 7.7 | 8.98 | 9.85 | ||||||||||||||||
| Per share market value, end of year | $ 6.71 | $ 6.99 | $ 6.58 | $ 5.46 | $ 6.49 | ||||||||||||||||
| Total return | [3] | 10.21% | 20.54% | 13.64% | (8.42%) | 120.98% | |||||||||||||||
| Shares outstanding at end of year | 65,296,094 | 65,296,094 | 65,224,500 | 65,224,500 | 67,045,105 | ||||||||||||||||
| Ratios / Supplemental Data: | |||||||||||||||||||||
| Ratio of operating expenses to average net assets | [4] | 7.13% | 7.73% | 7.75% | 4.17% | 3.74% | |||||||||||||||
| Ratio of interest and expenses on debt to average net assets | [5] | 8.56% | 9.06% | 7.55% | 5.19% | 3.73% | |||||||||||||||
| Ratio of total expenses to average net assets | [5] | 15.69% | 16.78% | 15.30% | 9.36% | 7.47% | |||||||||||||||
| Ratio of net investment income to average net assets | [5] | 9.47% | 12.04% | 12.56% | 6.74% | 6.04% | |||||||||||||||
| Net Assets at end of year | $ 463,950 | $ 493,908 | $ 502,187 | $ 585,565 | $ 660,144 | ||||||||||||||||
| Weighted average debt outstanding | [6] | $ 686,808 | $ 693,573 | $ 656,776 | $ 695,267 | $ 649,666 | |||||||||||||||
| Weighted average debt per share | [1],[6] | $ 10.52 | $ 10.63 | $ 10.07 | $ 10.49 | $ 9.69 | |||||||||||||||
| Asset coverage per unit | [7] | $ 1,627 | $ 1,637 | $ 1,952 | $ 1,855 | $ 2,208 | |||||||||||||||
| Average market value per unit | [8] | $ 0 | $ 0 | $ 0 | $ 0 | $ 25.13 | |||||||||||||||
| Portfolio turnover ratio | 65.30% | 43.99% | 32.58% | 70.41% | 37.74% | ||||||||||||||||
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