Annual report [Section 13 and 15(d), not S-K Item 405]

NET INCREASE (DECREASE) IN NET ASSETS RESULTING FROM OPERATIONS PER COMMON SHARE (Details)

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NET INCREASE (DECREASE) IN NET ASSETS RESULTING FROM OPERATIONS PER COMMON SHARE (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2023
Earnings Per Share [Abstract]      
Numerator for basic net increase (decrease) in net assets resulting from operations per common share (in shares) $ 57,191 $ 94,506 $ 42,668
Denominator for basic weighted average common shares (in shares) [1] 22,357,574 21,781,074 18,657,961
Basic net increase (decrease) in net assets resulting from operations per common share (in USD per share) [1] $ 2.56 $ 4.34 $ 2.29
Adjustment for interest and amortization on 2030 Convertible Notes $ 517 $ 0 $ 0
Numerator for diluted net increase (decrease) in net assets resulting from operations per common share $ 57,708 $ 94,506 $ 42,668
Adjustment for dilutive effect of 2030 Convertible Notes (in shares) 304,623 0 0
Denominator for diluted weighted average common shares (in shares) [1] 22,662,197 21,781,074 18,657,961
Diluted net increase (decrease) in net assets resulting from operations per common share (in USD per share) [1] $ 2.55 $ 4.34 $ 2.29
[1] Per share amounts and weighted average common shares outstanding have been adjusted on a retroactive basis to reflect the Reverse Stock Split effected on April 4, 2024. Refer to Note 2—Summary of Significant Accounting Policies for additional information.