Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Schedule of Fair Value Measurements Using Significant Unobservable Inputs (Details)

v3.26.1
INVESTMENTS - Schedule of Fair Value Measurements Using Significant Unobservable Inputs (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Total        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance $ 901,839 $ 757,625 $ 854,013 $ 796,222
New investments, repayments and settlements:        
Issuances/originations 83,621 74,031 230,473 268,103
Settlements/repayments (40,153) (80,934) (136,866) (238,417)
Net proceeds from sales 0 (731) (3,025) (89,564)
Transfers   0   0
Ending balance 948,381 746,214 948,381 746,214
Change in unrealized appreciation (depreciation) attributable to investments still held 3,639 (6,417) 4,953 613
Total | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 0 (3,708) 1,465 61,718
Total | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 3,639 (6,417) 5,632 3,659
Reversal of prior period net depreciation (appreciation) on realization (565) 6,348 (3,311) (55,507)
Secured First Lien Debt        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 630,527 541,524 622,371 554,937
New investments, repayments and settlements:        
Issuances/originations 73,304 73,889 159,694 212,754
Settlements/repayments (38,451) (80,193) (114,915) (221,130)
Net proceeds from sales 0 0 0 0
Transfers   (8,500)   (8,500)
Ending balance 665,834 529,149 665,834 529,149
Change in unrealized appreciation (depreciation) attributable to investments still held 1,019 815 (294) (8,899)
Secured First Lien Debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 0 (4,439) (325) (8,513)
Secured First Lien Debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 1,019 815 385 (10,011)
Reversal of prior period net depreciation (appreciation) on realization (565) 6,053 (1,376) 9,612
Secured second lien debt        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 185,141 144,970 150,542 113,716
New investments, repayments and settlements:        
Issuances/originations 2,591 130 58,004 47,827
Settlements/repayments (1,702) (741) (21,951) (17,287)
Net proceeds from sales 0 0 0 0
Transfers   0   0
Ending balance 185,844 144,299 185,844 144,299
Change in unrealized appreciation (depreciation) attributable to investments still held (186) (355) (606) (399)
Secured second lien debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 0 0 0 0
Secured second lien debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) (186) (355) (606) (252)
Reversal of prior period net depreciation (appreciation) on realization 0 295 (145) 295
Unsecured debt        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 341 335 333 32
New investments, repayments and settlements:        
Issuances/originations 13 12 39 345
Settlements/repayments 0 0 0 0
Net proceeds from sales 0 0 0 0
Transfers   0   0
Ending balance 356 354 356 354
Change in unrealized appreciation (depreciation) attributable to investments still held 2 7 (16) (23)
Unsecured debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 0 0 0 0
Unsecured debt | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 2 7 (16) (23)
Reversal of prior period net depreciation (appreciation) on realization 0 0 0 0
Preferred Equity        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 37,394 25,031 31,214 31,346
New investments, repayments and settlements:        
Issuances/originations 2,000 0 6,940 6,262
Settlements/repayments 0 0 0 0
Net proceeds from sales 0 0 0 (19,404)
Transfers   0   0
Ending balance 40,876 25,717 40,876 25,717
Change in unrealized appreciation (depreciation) attributable to investments still held 1,482 686 2,722 7,513
Preferred Equity | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 0 0 0 5,404
Preferred Equity | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 1,482 686 2,722 7,513
Reversal of prior period net depreciation (appreciation) on realization 0 0 0 (5,404)
Common Equity/ Equivalents        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 48,436 45,765 49,553 96,191
New investments, repayments and settlements:        
Issuances/originations 5,713 0 5,796 915
Settlements/repayments 0 0 0 0
Net proceeds from sales 0 (731) (3,025) (70,160)
Transfers   8,500   8,500
Ending balance 55,471 46,695 55,471 46,695
Change in unrealized appreciation (depreciation) attributable to investments still held 1,322 (7,570) 3,147 2,421
Common Equity/ Equivalents | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 0 731 1,790 64,827
Common Equity/ Equivalents | Location, Statement of Income, Balance [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) 1,322 (7,570) 3,147 6,432
Reversal of prior period net depreciation (appreciation) on realization $ 0 $ 0 $ (1,790) $ (60,010)