Quarterly report pursuant to Section 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, 2024
Mar. 31, 2023
Mar. 31, 2024
Mar. 31, 2023
Sep. 30, 2023
Debt Instrument [Line Items]          
Line of credit at fair value (Cost of $117,200 and $47,800, respectively) $ 117,200   $ 117,200   $ 47,800
Significant Unobservable Inputs (Level 3) | Fair Value, Recurring          
Debt Instrument [Line Items]          
Line of credit at fair value (Cost of $117,200 and $47,800, respectively) 117,200   117,200   $ 47,800
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 85,000 $ 108,400 47,800 $ 141,800  
Borrowings 64,100 85,600 134,300 100,400  
Repayments (31,900) (41,400) (64,900) (89,600)  
Net unrealized appreciation 0 (161) 0 (161)  
Ending balance $ 117,200 $ 152,439 $ 117,200 $ 152,439