Quarterly report [Sections 13 or 15(d)]

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

v3.25.3
INVESTMENTS - Schedule of Changes in Level 3 Fair Value Measurements of Investments (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2024
Mar. 31, 2024
New investments, repayments and settlements:                
Investments, cost $ 1,037,200   $ 1,037,200     $ 939,066 [1]    
PSI Molded                
New investments, repayments and settlements:                
Investments, cost         $ 10,600      
Total                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 1,125,784 $ 853,307 1,125,784 $ 853,307 1,031,735 974,345 $ 899,138 $ 920,486
New investments, repayments and settlements:                
Issuances / originations 71,036 19,500 133,878 20,098        
Settlements / repayments (1,436) (25,000) (5,806) (28,000)        
Sales 0 (48,503) 0 (48,503)        
Transfers 0 0 0 0        
Ending balance 1,125,784 853,307 1,125,784 853,307        
Total | Debt and Equity Securities, Realized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) (29,938) 42,284 (29,938) 42,284        
Total | Debt and Equity Securities, Unrealized Gain (Loss)                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 35,283 3,916 34,201 (15,030)        
Reversal of previously recorded (appreciation) depreciation upon realization 19,104 (38,028) 19,104 (38,028)        
Secured First Lien Debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 593,979 469,480 593,979 469,480 557,057 514,334 463,219 474,856
New investments, repayments and settlements:                
Issuances / originations 49,936 19,500 95,876 20,098        
Settlements / repayments (1,436) 0 (5,806) (3,000)        
Sales 0 0 0 0        
Transfers 0 0 0 0        
Ending balance 593,979 469,480 593,979 469,480        
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) (29,938) 0 (29,938) 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) (744) (13,239) 409 (22,474)        
Reversal of previously recorded (appreciation) depreciation upon realization 19,104 0 19,104 0        
Secured Second Lien Debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 90,633 111,344 90,633 111,344 93,340 103,580 137,827 138,703
New investments, repayments and settlements:                
Issuances / originations 0 0 0 0        
Settlements / repayments 0 (25,000) 0 (25,000)        
Sales 0 0 0 0        
Transfers 0 0 (10,616) 0        
Ending balance 90,633 111,344 90,633 111,344        
Secured Second Lien Debt | PSI Molded                
New investments, repayments and settlements:                
Investments, cost 10,600   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 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) (2,707) (1,483) (2,331) (2,359)        
Reversal of previously recorded (appreciation) depreciation upon realization 0 0 0 0        
Preferred Equity                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 365,278 228,528 365,278 228,528 325,997 302,163 212,591 213,480
New investments, repayments and settlements:                
Issuances / originations 21,100 0 38,002 0        
Settlements / repayments 0 0 0 0        
Sales 0 0 0 0        
Transfers 0 0 10,616 0        
Ending balance 365,278 228,528 365,278 228,528        
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 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) 18,181 15,937 14,497 15,048        
Reversal of previously recorded (appreciation) depreciation upon realization 0 0 0 0        
Common Equity/ Equivalents                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 75,894 43,955 75,894 43,955 $ 55,341 $ 54,268 $ 85,501 $ 93,447
New investments, repayments and settlements:                
Issuances / originations 0 0 0 0        
Settlements / repayments 0 0 0 0        
Sales 0 (48,503) 0 (48,503)        
Transfers 0 0 0 0        
Ending balance 75,894 43,955 75,894 43,955        
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 42,284 0 42,284        
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) 20,553 2,701 21,626 (5,245)        
Reversal of previously recorded (appreciation) depreciation upon realization $ 0 $ (38,028) $ 0 $ (38,028)        
[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.