Annual report [Section 13 and 15(d), not S-K Item 405]

INVESTMENTS - Schedule of Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details)

v3.25.3
INVESTMENTS - Schedule of Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Total    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance $ 796,222 $ 704,562
New investments, repayments and settlements:    
Issuances/originations 396,706 183,175
Settlements/repayments (261,907) (133,641)
Net proceeds from sales (89,564) (2,776)
Transfers 0 0
Ending balance 854,013 796,222
Total | Net realized gain (loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 55,368 2,006
Total | Net unrealized appreciation (depreciation) and Reversal of prior period net depreciation (appreciation) on realization    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 6,345 43,124
Reversal of prior period net depreciation (appreciation) on realization (49,157) (228)
Secured First Lien Debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 554,937 510,701
New investments, repayments and settlements:    
Issuances/originations 322,603 131,462
Settlements/repayments (240,195) (80,102)
Net proceeds from sales 0 50
Transfers (8,500) 0
Ending balance 622,371 554,937
Secured First Lien Debt | Net realized gain (loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) (8,513) (50)
Secured First Lien Debt | Net unrealized appreciation (depreciation) and Reversal of prior period net depreciation (appreciation) on realization    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) (7,573) (7,071)
Reversal of prior period net depreciation (appreciation) on realization 9,612 (53)
Secured second lien debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 113,716 127,854
New investments, repayments and settlements:    
Issuances/originations 57,958 36,978
Settlements/repayments (21,712) (53,539)
Net proceeds from sales 0 0
Transfers 0 0
Ending balance 150,542 113,716
Secured second lien debt | Net realized gain (loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 0 0
Secured second lien debt | Net unrealized appreciation (depreciation) and Reversal of prior period net depreciation (appreciation) on realization    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 285 2,445
Reversal of prior period net depreciation (appreciation) on realization 295 (22)
Unsecured debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 32 24
New investments, repayments and settlements:    
Issuances/originations 357 0
Settlements/repayments 0 0
Net proceeds from sales 0 0
Transfers 0 0
Ending balance 333 32
Unsecured debt | Net realized gain (loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 0 0
Unsecured debt | Net unrealized appreciation (depreciation) and Reversal of prior period net depreciation (appreciation) on realization    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) (56) 8
Reversal of prior period net depreciation (appreciation) on realization 0 0
Preferred equity    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 31,346 26,855
New investments, repayments and settlements:    
Issuances/originations 12,762 10,150
Settlements/repayments 0 0
Net proceeds from sales (19,404) (1,082)
Transfers 0 0
Ending balance 31,214 31,346
Preferred equity | Net realized gain (loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) (946) 332
Preferred equity | Net unrealized appreciation (depreciation) and Reversal of prior period net depreciation (appreciation) on realization    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 6,510 (5,039)
Reversal of prior period net depreciation (appreciation) on realization 946 130
Common Equity/ Equivalents    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 96,191 39,128
New investments, repayments and settlements:    
Issuances/originations 3,026 4,585
Settlements/repayments 0 0
Net proceeds from sales (70,160) (1,744)
Transfers 8,500 0
Ending balance 49,553 96,191
Common Equity/ Equivalents | Net realized gain (loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 64,827 1,724
Common Equity/ Equivalents | Net unrealized appreciation (depreciation) and Reversal of prior period net depreciation (appreciation) on realization    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 7,179 52,781
Reversal of prior period net depreciation (appreciation) on realization $ (60,010) $ (283)