v3.26.1
Fair Value of Financial Instruments - Summary of Unobservable Inputs and Ranges (Details)
$ in Thousands
Jun. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
First lien | Market Comparable | Revenue Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.007  
First lien | Market Comparable | Revenue Multiple | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.009  
First lien | Market Comparable | Revenue Multiple | Weighted Average    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.009  
Level 3    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 2,424,209 $ 2,729,010
Level 3 | Long-Term Credit Facility | Market Comparable | Market Yield    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 318,310 $ 683,837
Range of Input 0.054 [1] 0.048 [2]
Level 3 | Subordinated Debt | Market Comparable | Market Yield    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 13,575  
Range of Input [1] 0.139  
Level 3 | Subordinated Debt | Market Comparable | Market Yield | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.112  
Level 3 | Subordinated Debt | Market Comparable | Market Yield | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.164  
Level 3 | Subordinated Debt | Enterprise Market Value | EBITDA Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 3,995  
Level 3 | Subordinated Debt | Enterprise Market Value | EBITDA Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.075  
Level 3 | Subordinated Debt | Enterprise Market Value | EBITDA Multiple | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.303  
Level 3 | Subordinated Debt | Enterprise Market Value | EBITDA Multiple | Weighted Average    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.272  
Level 3 | Subordinated Debt | Enterprise Market Value | Revenue Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 2,114  
Level 3 | Subordinated Debt | Enterprise Market Value | Revenue Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.006  
Level 3 | Subordinated Debt | Enterprise Market Value | Revenue Multiple | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0  
Level 3 | Subordinated Debt | Enterprise Market Value | Revenue Multiple | Weighted Average    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.006  
Level 3 | First lien | Market Comparable | Broker/Dealer Bids or Quotes    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 88,413 $ 114,625
Level 3 | First lien | Market Comparable | Market Yield    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 2,102,418 $ 2,377,201
Level 3 | First lien | Market Comparable | Market Yield | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input 0.078 [1] 0.04 [2]
Level 3 | First lien | Market Comparable | Market Yield | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input 0.216 [1] 0.245 [2]
Level 3 | First lien | Market Comparable | Market Yield | Weighted Average    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input 0.10 [1] 0.099 [2]
Level 3 | First lien | Market Comparable | EBITDA Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [2]   0.083
Level 3 | First lien | Market Comparable | Revenue Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value   $ 3,836
Level 3 | First lien | Market Comparable | Revenue Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [2]   0.006
Level 3 | First lien | Enterprise Market Value | EBITDA Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 34,059 $ 17,969
Range of Input [1] 0.004  
Level 3 | First lien | Enterprise Market Value | EBITDA Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.06  
Level 3 | First lien | Enterprise Market Value | EBITDA Multiple | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.178  
Level 3 | First lien | Enterprise Market Value | Revenue Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 5,806  
Level 3 | Second lien | Market Comparable | Broker/Dealer Bids or Quotes    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value   995
Level 3 | Second lien | Market Comparable | Market Yield    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value   $ 17,439
Range of Input [2]   0.171
Level 3 | Second lien | Market Comparable | Market Yield | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [2]   0.07
Level 3 | Second lien | Market Comparable | Market Yield | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [2]   0.254
Level 3 | Second lien | Enterprise Market Value | EBITDA Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value   $ 547
Range of Input [2]   0.148
Level 3 | Equity | Enterprise Market Value | EBITDA Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 173,300 $ 196,398
Level 3 | Equity | Enterprise Market Value | EBITDA Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input 0.045 [1] 0.006 [2]
Level 3 | Equity | Enterprise Market Value | EBITDA Multiple | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input 0.178 [1] 0.283 [2]
Level 3 | Equity | Enterprise Market Value | EBITDA Multiple | Weighted Average    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input 0.105 [1] 0.108 [2]
Level 3 | Equity | Enterprise Market Value | Revenue Multiple    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Fair value $ 529  
Level 3 | Equity | Enterprise Market Value | Revenue Multiple | Minimum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.005  
Level 3 | Equity | Enterprise Market Value | Revenue Multiple | Maximum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.013  
Level 3 | Equity | Enterprise Market Value | Revenue Multiple | Weighted Average    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]    
Range of Input [1] 0.003  
[1] The weighted averages disclosed in the table above were weighted by their relative fair value.
[2] The weighted averages disclosed in the table above were weighted by their relative fair value.