v3.26.1
Investments - Schedule of Investments (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Principal $ 7,846,235 $ 8,253,915
Amortized Cost 8,377,113 8,759,938
Fair Value 8,196,353 [1] 8,769,389 [2]
Senior secured    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Principal 400,105 448,400
Amortized Cost 396,798 444,061
Fair Value 391,132 442,477
One stop    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Principal 7,381,116 7,735,754
Amortized Cost 7,288,781 7,633,999
Fair Value 7,162,462 7,615,809
Second lien    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Principal 28,420 31,317
Amortized Cost 26,598 29,607
Fair Value 22,877 26,409
Subordinated debt    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Principal 36,594 38,444
Amortized Cost 36,407 38,027
Fair Value 36,171 38,412
Equity    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost 628,529 614,244
Fair Value $ 583,711 $ 646,282
[1] The fair values of investments were valued using significant unobservable inputs, unless noted otherwise. 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 noted otherwise. See Note 6. The fair value of loan investments may include the impact of the unfunded commitment being valued below par.