v3.26.1
Investments - Schedule of Fair Value, Assets Measured on Recurring Basis (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Schedule of Investments [Line Items]    
Principal $ 9,719,706 $ 8,521,763
Amortized Cost 9,727,658 8,479,341
Fair Value 9,616,525 [1] 8,555,251 [2]
Senior secured    
Schedule of Investments [Line Items]    
Principal 1,787,827 2,288,864
Amortized Cost 1,782,952 2,283,507
Fair Value 1,712,492 2,285,901
One stop    
Schedule of Investments [Line Items]    
Principal 7,614,494 5,978,203
Amortized Cost 7,530,093 5,881,309
Fair Value 7,490,815 5,948,840
Second lien    
Schedule of Investments [Line Items]    
Principal 28,490 35,084
Amortized Cost 28,338 34,869
Fair Value 28,205 35,084
Subordinated debt    
Schedule of Investments [Line Items]    
Principal 61,870 58,087
Amortized Cost 62,209 57,122
Fair Value 60,761 57,646
Structured finance notes    
Schedule of Investments [Line Items]    
Principal 227,025 161,525
Amortized Cost 226,923 161,487
Fair Value 224,585 162,943
Equity    
Schedule of Investments [Line Items]    
Amortized Cost 97,143 61,047 [3],[4]
Fair Value $ 99,667 $ 64,837 [2],[3],[4]
[1] The fair values of investments were valued using significant unobservable inputs, unless otherwise noted. See Note 6. 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 6. The fair value of loan investments may include the impact of the unfunded commitment being valued below par.
[3] Equity investments are non-income producing securities, unless otherwise noted.
[4] Ownership of certain equity investments occurs through a holding company or partnership.