Quarterly report [Sections 13 or 15(d)]

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

v3.26.3
INVESTMENTS - Schedule of Changes in Level 3 Fair Value Measurements of Investments (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
New investments, repayments and settlements:                
Cost $ 1,181,079   $ 1,181,079     $ 1,052,848 [1]    
Total                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 1,425,975 $ 1,125,784 1,425,975 $ 1,125,784 $ 1,277,075 1,304,243 $ 1,031,735 $ 974,345
New investments, repayments and settlements:                
Issuances / originations 156,493 71,036 157,093 133,878        
Settlements / repayments (19,862) (1,436) (19,862) (5,806)        
Sales 0 0 0 0        
Transfers 0 0 0 0        
Ending balance 1,425,975 1,125,784 1,425,975 1,125,784        
Change in unrealized (depreciation) appreciation attributable to investments still held 12,269 35,283 (10,120) 34,201        
Total | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 0 (29,938) (9,000) (29,938)        
Total | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 12,269 35,283 (10,120) 34,201        
Reversal of previously recorded (appreciation) depreciation upon realization 0 19,104 3,621 19,104        
Secured First Lien Debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 654,079 593,979 654,079 593,979 564,631 570,602 557,057 514,334
New investments, repayments and settlements:                
Issuances / originations 113,888 49,936 113,888 95,876        
Settlements / repayments (19,862) (1,436) (19,862) (5,806)        
Sales 0 0 0 0        
Transfers 0 0 0 0        
Ending balance 654,079 593,979 654,079 593,979        
Change in unrealized (depreciation) appreciation attributable to investments still held (4,578) (744) (5,170) 409        
Secured First Lien Debt | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 0 (29,938) (9,000) (29,938)        
Secured First Lien Debt | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) (4,578) (744) (5,170) 409        
Reversal of previously recorded (appreciation) depreciation upon realization 0 19,104 3,621 19,104        
Secured Second Lien Debt                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Beginning balance 107,333 90,633 107,333 90,633 102,789 99,197 93,340 103,580
New investments, repayments and settlements:                
Issuances / originations 0 0 600 0        
Settlements / repayments 0 0 0 0        
Sales 0 0 0 0        
Transfers 0 0 0 (10,616)        
Ending balance 107,333 90,633 107,333 90,633        
Change in unrealized (depreciation) appreciation attributable to investments still held 4,544 (2,707) 7,536 (2,331)        
Secured Second Lien Debt | PSI Molded                
New investments, repayments and settlements:                
Cost             10,600  
Secured Second Lien Debt | Income Statement Location [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 | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 4,544 (2,707) 7,536 (2,331)        
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 484,076 365,278 484,076 365,278 429,510 426,949 325,997 302,163
New investments, repayments and settlements:                
Issuances / originations 42,605 21,100 42,605 38,002        
Settlements / repayments 0 0 0 0        
Sales 0 0 0 0        
Transfers 0 0 0 10,616        
Ending balance 484,076 365,278 484,076 365,278        
Change in unrealized (depreciation) appreciation attributable to investments still held 11,961 18,181 14,522 14,497        
Preferred Equity | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 0 0 0 0        
Preferred Equity | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 11,961 18,181 14,522 14,497        
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 180,487 75,894 180,487 75,894 $ 180,145 $ 207,495 $ 55,341 $ 54,268
New investments, repayments and settlements:                
Issuances / originations 0 0 0 0        
Settlements / repayments 0 0 0 0        
Sales 0 0 0 0        
Transfers 0 0 0 0        
Ending balance 180,487 75,894 180,487 75,894        
Change in unrealized (depreciation) appreciation attributable to investments still held 342 20,553 (27,008) 21,626        
Common Equity/ Equivalents | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesRealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 0 0 0 0        
Common Equity/ Equivalents | Income Statement Location [Axis]: us-gaap:DebtAndEquitySecuritiesUnrealizedGainLoss                
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]                
Total gain (loss) 342 20,553 (27,008) 21,626        
Reversal of previously recorded (appreciation) depreciation upon realization $ 0 $ 0 $ 0 $ 0        
[1] Cumulative gross unrealized appreciation for federal income tax purposes is $428.5 million; cumulative gross unrealized depreciation for federal income tax purposes is $173.7 million. Cumulative net unrealized appreciation is $254.8 million, based on a tax cost of $1.1 billion.