Quarterly report [Sections 13 or 15(d)]

INVESTMENTS - Narrative (Details)

v3.25.3
INVESTMENTS - Narrative (Details)
$ in Thousands
 1 Months Ended 3 Months Ended 6 Months Ended
Sep. 30, 2025
USD ($)
industry
portfolioCompany
state
Jul. 31, 2025
USD ($)
May 31, 2025
USD ($)
Sep. 30, 2025
USD ($)
industry
portfolioCompany
state
Sep. 30, 2024
USD ($)
Sep. 30, 2025
USD ($)
industry
portfolioCompany
state
Sep. 30, 2024
USD ($)
Aug. 31, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Summary of Investment Holdings [Line Items]                    
Purchase of investments           $ 133,878 $ 20,098      
Investments, cost $ 1,037,200     $ 1,037,200   1,037,200       $ 939,066 [1]
Net realized gain (loss)       $ (29,938) $ 42,303 $ (29,938) $ 42,305      
Number of investment portfolio company | portfolioCompany 28     28   28        
Number of states or countries which have invested in the company location | state 20     20   20        
Number of industries that have made investments | industry 16     16   16        
Investments owned, fair value $ 1,130,859     $ 1,130,859   $ 1,130,859       979,320 [1]
Uncollectible receivables allowance, minimum required day for uncollectible adjustment           90 days        
Gross receivables from portfolio companies 2,400     2,400   $ 2,400       2,300
Allowance for uncollectible receivables 1,400     1,400   1,400       1,700
Five Largest Portfolio Investments | Investment Portfolio Benchmark | Customer Concentration Risk                    
Summary of Investment Holdings [Line Items]                    
Investments owned, fair value 437,400     437,400   $ 437,400        
Percentage of total investments           38.70%        
Secured First Lien Debt                    
Summary of Investment Holdings [Line Items]                    
Investments, cost 644,158     644,158   $ 644,158       584,026
Investments owned, fair value 593,979     593,979   593,979       514,334
Preferred Equity                    
Summary of Investment Holdings [Line Items]                    
Investments, cost 250,105     250,105   250,105       201,487
Investments owned, fair value 365,278     $ 365,278   $ 365,278       $ 302,163
Smart Chemical                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments     $ 49,500              
Smart Chemical | Secured First Lien Debt                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments     35,700              
Smart Chemical | Preferred Equity                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments     13,800              
Sun State                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments     12,800              
Sun State | Secured First Lien Debt                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments     9,800              
Sun State | Preferred Equity                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments     $ 3,100              
PSI Molded                    
Summary of Investment Holdings [Line Items]                    
Investments, cost                 $ 10,600  
Global GRAB Technologies, Inc., ("Global GRAB")                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments   $ 67,600                
Global GRAB Technologies, Inc., ("Global GRAB") | Secured First Lien Debt                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments   46,500                
Global GRAB Technologies, Inc., ("Global GRAB") | Preferred Equity                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments   $ 21,100                
J.R. Hobbs                    
Summary of Investment Holdings [Line Items]                    
Purchase of investments 20,000                  
Investments, cost               $ 49,900    
Net realized gain (loss) $ (29,900)                  
[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.