Financial Highlights - Summary of Financial Highlights (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||||||||||||||||||||
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Sep. 30, 2023 |
Sep. 30, 2022 |
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2019 |
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Investment Company, Financial Highlights [Abstract] | |||||||||||||||||||||
Net Asset Value Per Share, Beginning Balance | $ 11.62 | [1] | $ 12.62 | $ 12.31 | $ 12.97 | $ 13.82 | |||||||||||||||
Net investment income | [2] | 1.33 | 1.18 | 1.02 | 1.12 | 1.17 | |||||||||||||||
Net change in realized and unrealized (loss) gain | [2] | (0.56) | (1.1) | 0.44 | (0.65) | (0.88) | |||||||||||||||
Net increase in net assets resulting from operations | [2] | 0.77 | 0.08 | 1.46 | 0.47 | 0.29 | |||||||||||||||
Distribution of net investment income | [2],[3] | (1.19) | (1.14) | (1.14) | (1.14) | (1.14) | |||||||||||||||
Distribution of realized gains | [2],[3] | 0 | 0 | 0 | 0 | 0 | |||||||||||||||
Total distributions to stockholders | [2],[3] | (1.19) | (1.14) | (1.14) | (1.14) | (1.14) | |||||||||||||||
(Dilutive) effect of common stock issuance | (0.08) | 0.06 | 0 | 0 | 0 | ||||||||||||||||
Net Asset Value Per Share, Ending Balance | 11.13 | [1] | 11.62 | [1] | 12.62 | 12.31 | 12.97 | ||||||||||||||
Per share market value, end of year | $ 10.66 | $ 9.6 | $ 12.79 | $ 8.44 | $ 11.6 | ||||||||||||||||
Total return | [4] | 23.84% | (17.76%) | 66.47% | (17.15%) | (3.20%) | |||||||||||||||
Shares outstanding at end of year | 58,734,702 | 45,345,638 | 38,880,728 | 38,772,074 | 38,772,074 | ||||||||||||||||
Ratios / Supplemental Data: | |||||||||||||||||||||
Ratio of operating expenses to average net assets | [5] | 5.90% | 5.34% | 3.77% | 5.19% | 3.94% | |||||||||||||||
Ratio of debt related expenses to average net assets | [6] | 6.68% | 5.85% | 5.00% | 5.63% | 5.21% | |||||||||||||||
Ratio of total expenses to average net assets | [6] | 12.58% | 11.19% | 8.77% | 10.82% | 9.15% | |||||||||||||||
Ratio of net investment income to average net assets | [6] | 11.82% | 9.55% | 8.07% | 9.00% | 8.76% | |||||||||||||||
Net assets at end of year | $ 653,605 | $ 527,092 | $ 490,611 | $ 477,270 | $ 503,057 | ||||||||||||||||
Weighted average debt outstanding | $ 615,068 | $ 698,765 | $ 622,739 | $ 737,209 | $ 512,135 | ||||||||||||||||
Weighted average debt per share | [2] | $ 12.1 | $ 17.06 | $ 16.06 | $ 19.01 | $ 13.21 | |||||||||||||||
Asset coverage per unit | [7] | $ 2,304 | $ 1,784 | $ 1,746 | $ 1,677 | $ 1,786 | |||||||||||||||
Portfolio turnover ratio | 28.64% | 45.03% | 62.58% | 35.08% | 52.64% | ||||||||||||||||
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