Quarterly report [Sections 13 or 15(d)]

BORROWINGS - Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details)

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BORROWINGS - Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Sep. 30, 2024
Debt Instrument [Line Items]          
Line of credit at fair value (Cost of $25,100 and $70,600, respectively) $ 25,149   $ 25,149   $ 70,600
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring          
Debt Instrument [Line Items]          
Line of credit at fair value (Cost of $25,100 and $70,600, respectively) 25,149   25,149   $ 70,600
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring | Long-Term Debt          
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]          
Beginning balance 61,500 $ 85,000 70,600 $ 47,800  
Borrowings 61,000 64,100 148,500 134,300  
Repayments (97,400) (31,900) (194,000) (64,900)  
Net unrealized appreciation 49 0 49 0  
Ending balance $ 25,149 $ 117,200 $ 25,149 $ 117,200