Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Schedule of Changes in Level 3 Fair Value Measurements of Investments (Details)

v3.25.2
INVESTMENTS - Schedule of Changes in Level 3 Fair Value Measurements of Investments (Details) - USD ($)
$ in Thousands
 3 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Mar. 31, 2025
Mar. 31, 2024
New investments, repayments and settlements:        
Cost $ 997,538   $ 939,066 [1]  
PSI Molded        
New investments, repayments and settlements:        
Cost 10,600      
Total        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 1,031,735 $ 899,138 974,345 $ 920,486
New investments, repayments and settlements:        
Issuances / originations 62,842 598    
Settlements / repayments (4,370) (3,000)    
Sales 0 0    
Transfers 0 0    
Ending balance 1,031,735 899,138    
Total | 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    
Total | Debt and Equity Securities, Unrealized Gain (Loss)        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Total gain (loss) (1,082) (18,946)    
Reversal of previously recorded (appreciation) depreciation upon realization 0 0    
Secured First Lien Debt        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 557,057 463,219 514,334 474,856
New investments, repayments and settlements:        
Issuances / originations 45,941 598    
Settlements / repayments (4,370) (3,000)    
Sales 0 0    
Transfers 0 0    
Ending balance 557,057 463,219    
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) 0 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) 1,152 (9,235)    
Reversal of previously recorded (appreciation) depreciation upon realization 0 0    
Secured Second Lien Debt        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 93,340 137,827 103,580 138,703
New investments, repayments and settlements:        
Issuances / originations 0 0    
Settlements / repayments 0 0    
Sales 0 0    
Transfers (10,616) 0    
Ending balance 93,340 137,827    
Secured Second Lien Debt | PSI Molded        
New investments, repayments and settlements:        
Cost 10,600      
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) 376 (876)    
Reversal of previously recorded (appreciation) depreciation upon realization 0 0    
Preferred Equity        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 325,997 212,591 302,163 213,480
New investments, repayments and settlements:        
Issuances / originations 16,901 0    
Settlements / repayments 0 0    
Sales 0 0    
Transfers 10,616 0    
Ending balance 325,997 212,591    
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) 0 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) (3,683) (889)    
Reversal of previously recorded (appreciation) depreciation upon realization 0 0    
Common Equity/ Equivalents        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning balance 55,341 85,501 $ 54,268 $ 93,447
New investments, repayments and settlements:        
Issuances / originations 0 0    
Settlements / repayments 0 0    
Sales 0 0    
Transfers 0 0    
Ending balance 55,341 85,501    
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) 0 0    
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) 1,073 (7,946)    
Reversal of previously recorded (appreciation) depreciation upon realization $ 0 $ 0    
[1] Cumulative gross unrealized appreciation for federal income tax purposes is $183.3 million; cumulative gross unrealized depreciation for federal income tax purposes is $144.9 million. Cumulative net unrealized appreciation is $38.5 million, based on a tax cost of $940.9 million.