v3.26.1
Fair Value Measurements - Schedule of Fair Value Measurement Inputs and Valuation Techniques (Details)
$ in Thousands
Jun. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 2,667,489 [1] $ 2,209,174 [2]
Equity    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value 41,121 35,130
Level 3 | Senior secured loans | Valuation, Yield Analysis And Market Comparable Companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 120,063 $ 77,408
Level 3 | Senior secured loans | Minimum | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.085 0.073
Level 3 | Senior secured loans | Minimum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 5.5 6.0
Level 3 | Senior secured loans | Maximum | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.103 0.090
Level 3 | Senior secured loans | Maximum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 20.5 20.0
Level 3 | Senior secured loans | Weighted Average | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.088 0.083
Level 3 | Senior secured loans | Weighted Average | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 10.6 10.6
Level 3 | One stop loans | Valuation, Yield Analysis And Market Comparable Companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 2,456,010 $ 2,043,193
Level 3 | One stop loans | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value 2,274 49
Level 3 | One stop loans | Broker/dealer bids or quotes    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value 24,718 19,980
Level 3 | One stop loans | EBITDA multiples | Valuation, Yield Analysis And Market Comparable Companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value 2,173,599 1,758,059
Level 3 | One stop loans | Revenue multiples | Valuation, Yield Analysis And Market Comparable Companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 282,411 $ 285,134
Level 3 | One stop loans | Minimum | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.075 0.038
Level 3 | One stop loans | Minimum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 7.5 8.0
Level 3 | One stop loans | Minimum | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 1.3 2.0
Level 3 | One stop loans | Maximum | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.210 0.205
Level 3 | One stop loans | Maximum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 29.3 33.0
Level 3 | One stop loans | Maximum | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 14.0 15.0
Level 3 | One stop loans | Weighted Average | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.095 0.086
Level 3 | One stop loans | Weighted Average | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 14.7 15.8
Level 3 | One stop loans | Weighted Average | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 8.2 9.1
Level 3 | Subordinated debt and second lien loans | Valuation, Yield Analysis And Market Comparable Companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 25,577 $ 33,463
Level 3 | Subordinated debt and second lien loans | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value   $ 66
Level 3 | Subordinated debt and second lien loans | Minimum | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.105 0.098
Level 3 | Subordinated debt and second lien loans | Minimum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 9.5 9.5
Level 3 | Subordinated debt and second lien loans | Maximum | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.135 0.150
Level 3 | Subordinated debt and second lien loans | Maximum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 21.0 24.0
Level 3 | Subordinated debt and second lien loans | Weighted Average | Market interest rate | Yield analysis    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 0.115 0.111
Level 3 | Subordinated debt and second lien loans | Weighted Average | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 18.4 17.8
Level 3 | Equity    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 41,121 $ 35,130
Level 3 | Equity | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value 41,121 35,130
Level 3 | Equity | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value 33,790 29,941
Level 3 | Equity | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 7,331 $ 5,189
Level 3 | Equity | Minimum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 5.5 8.0
Level 3 | Equity | Minimum | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 1.3 2.0
Level 3 | Equity | Maximum | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 26.0 28.0
Level 3 | Equity | Maximum | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 14.0 15.0
Level 3 | Equity | Weighted Average | EBITDA multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 16.1 17.4
Level 3 | Equity | Weighted Average | Revenue multiples | Market comparable companies    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Investment company, investment owned, measurement input 9.9 11.3
[1] The fair values of investments were valued using significant unobservable inputs, unless otherwise noted. See Note 7. The fair value of loan investments may include the impact of the unfunded commitment being valued below par.
[2] The fair values of investments were valued using significant unobservable inputs, unless otherwise noted. See Note 7. The fair value of loan investments may include the impact of the unfunded commitment being valued below par.