Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2024
USD ($)
investment
loan
Mar. 31, 2023
USD ($)
Mar. 31, 2024
USD ($)
investment
loan
Mar. 31, 2023
USD ($)
Sep. 30, 2023
USD ($)
loan
investment
Summary of Investment Holdings [Line Items]          
Cost $ 790,542   $ 790,542   $ 722,269 [1]
Fair Value 791,588   791,588   704,815 [1]
Total interest income (excluding PIK interest income) 22,330 $ 18,803 43,918 $ 36,172  
PIK interest income 1,385 775 2,793 1,773  
OID          
Summary of Investment Holdings [Line Items]          
Fair Value $ 900   $ 900   $ 700
Number of loans | loan 3   3   4
Total interest income (excluding PIK interest income) $ 100 100 $ 100 100  
PIK          
Summary of Investment Holdings [Line Items]          
Number of investments | investment 11   11   8
Proceeds from interest received $ 0 $ 0 $ 0 $ 400  
Edge Adhesives Holdings, Inc.          
Summary of Investment Holdings [Line Items]          
Cost $ 20,400   $ 20,400   $ 6,100
Cost percentage 2.80%   2.80%   0.90%
Fair Value $ 12,900   $ 12,900   $ 2,900
Fair value percentage 1.80%   1.80%   0.50%
[1] Cumulative gross unrealized depreciation for federal income tax purposes is $56.9 million; cumulative gross unrealized appreciation for federal income tax purposes is $33.7 million. Cumulative net unrealized depreciation is $23.2 million, based on a tax cost of $728.0 million.