Quarterly report pursuant to Section 13 or 15(d)

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

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INVESTMENTS - Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($)
$ in Thousands
 3 Months Ended
Dec. 31, 2024
Dec. 31, 2023
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 147,582 59,209
Settlements/repayments (92,096) (21,843)
Net proceeds from sales (73,081) (260)
Transfers 0 0
Ending balance 794,460 749,717
Total | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 57,724 259
Total | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 12,118 8,073
Reversal of prior period net depreciation (appreciation) on realization (54,009) (283)
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 111,754 50,024
Settlements/repayments (76,255) (21,119)
Net proceeds from sales 0 0
Transfers 0 0
Ending balance 586,409 546,602
Secured first lien debt | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) (4,074) 0
Secured first lien debt | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) (3,534) 6,996
Reversal of prior period net depreciation (appreciation) on realization 3,581 0
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 29,244 185
Settlements/repayments (15,841) (724)
Net proceeds from sales 0 0
Transfers 0 0
Ending balance 127,234 126,571
Secured second lien debt | Debt and Equity Securities, 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 | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 115 (744)
Reversal of prior period net depreciation (appreciation) on realization 0 0
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 322 0
Settlements/repayments 0 0
Net proceeds from sales 0 0
Transfers 0 0
Ending balance 359 23
Unsecured debt | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 0 0
Unsecured debt | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 5 (1)
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 6,262 9,000
Settlements/repayments 0 0
Net proceeds from sales (9,450) 0
Transfers 0 0
Ending balance 31,294 29,722
Preferred Equity | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 2,450 0
Preferred Equity | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 3,136 (6,133)
Reversal of prior period net depreciation (appreciation) on realization (2,450) 0
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 0 0
Settlements/repayments 0 0
Net proceeds from sales (63,631) (260)
Transfers 0 0
Ending balance 49,164 46,799
Common Equity/ Equivalents | Debt and Equity Securities, Realized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 59,348 259
Common Equity/ Equivalents | Debt and Equity Securities, Unrealized Gain (Loss)    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Total gain (loss) 12,396 7,955
Reversal of prior period net depreciation (appreciation) on realization $ (55,140) $ (283)