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 9 Months Ended
Jun. 30, 2026
USD ($)
loan
investment
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
segment
loan
investment
Jun. 30, 2025
USD ($)
Sep. 30, 2025
USD ($)
investment
Schedule of Investments [Line Items]          
Cost $ 968,661   $ 968,661   $ 876,614 [1]
Investments, at fair value 953,326   953,326   859,124 [1]
Total interest income (excluding PIK interest income) 22,829 $ 19,522 65,910 $ 60,517  
PIK interest income 1,465 1,331 $ 5,476 2,994  
Number of reportable segments | segment     1    
OID          
Schedule of Investments [Line Items]          
Investments, at fair value $ 600   $ 600   $ 200
Number of loans | loan 2   2    
Total interest income (excluding PIK interest income) $ 100 200 $ 200 400  
PIK          
Schedule of Investments [Line Items]          
Number of investments | investment 10   10   10
Proceeds from interest received $ 0 $ 0 $ 2,800 $ 7,200  
B+T Group Acquisition, Inc., Edge Adhesives Holdings, Inc,. And WB Xcel Holdings, LLC          
Schedule of Investments [Line Items]          
Cost $ 46,000   $ 46,000   $ 28,800
Cost percentage 5.20%   5.20%   3.60%
Investments, at fair value $ 26,700   $ 26,700   $ 13,000
Fair value percentage 3.10%   3.10%   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.