Quarterly report [Sections 13 or 15(d)]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)

v3.26.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2026
USD ($)
investment
loan
Mar. 31, 2025
USD ($)
Mar. 31, 2026
USD ($)
investment
segment
loan
Mar. 31, 2025
USD ($)
Sep. 30, 2025
USD ($)
investment
loan
Schedule of Investments [Line Items]          
Cost $ 925,193   $ 925,193   $ 876,614 [1]
Investments, at fair value 906,844   906,844   859,124 [1]
Total interest income (excluding PIK interest income) 21,486 $ 20,438 43,081 $ 40,995  
PIK interest income 1,710 900 $ 4,011 1,663  
Number of reportable segments | segment     1    
OID          
Schedule of Investments [Line Items]          
Investments, at fair value $ 800   $ 800   $ 200
Number of loans | loan 3   3   2
Total interest income (excluding PIK interest income) $ 52 100 $ 85 200  
PIK          
Schedule of Investments [Line Items]          
Number of investments | investment 9   9   9
Proceeds from interest received $ 3 $ 2,600 $ 2,800 $ 7,200  
B+T Group Acquisition, Inc., Edge Adhesives Holdings, Inc,. And WB Xcel Holdings, LLC          
Schedule of Investments [Line Items]          
Cost $ 28,800   $ 28,800   $ 28,800
Cost percentage 3.40%   3.40%   3.60%
Investments, at fair value $ 13,000   $ 13,000   $ 13,000
Fair value percentage 1.60%   1.60%   1.70%
[1] Cumulative gross unrealized depreciation for federal income tax purposes is $59.7 million; cumulative gross unrealized appreciation for federal income tax purposes is $34.1 million. Cumulative net unrealized depreciation is $25.5 million, based on a tax cost of $884.7 million.