v3.26.1
Fair Value Measurements - Schedule of Fair Value Measurements (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Assets, at fair value:    
Fair value $ 9,616,525 [1] $ 8,555,251 [2]
Money market funds 94,337 412,636
Forward currency contracts 2,277 388
Interest rate swaps 3,651 23,013
Total assets, at fair value: 9,716,790 8,991,288
Liabilities, at fair value:    
Forward currency contracts (4,023) (9,507)
Interest rate swaps (23,799) (3,121)
Total liabilities, at fair value: (27,822) (12,628)
Debt Investments    
Assets, at fair value:    
Fair value 9,516,858 8,490,414
Equity Investments    
Assets, at fair value:    
Fair value 99,667 64,837
Level 1    
Assets, at fair value:    
Money market funds 94,337 412,636
Forward currency contracts 0 0
Interest rate swaps 0 0
Total assets, at fair value: 94,337 412,636
Liabilities, at fair value:    
Forward currency contracts 0 0
Interest rate swaps 0 0
Total liabilities, at fair value: 0 0
Level 1 | Debt Investments    
Assets, at fair value:    
Fair value 0 0
Level 1 | Equity Investments    
Assets, at fair value:    
Fair value 0 0
Level 2    
Assets, at fair value:    
Fair value 1,276,609 1,750,395
Money market funds 0 0
Forward currency contracts 2,277 388
Interest rate swaps 3,651 23,013
Total assets, at fair value: 1,282,537 1,773,796
Liabilities, at fair value:    
Forward currency contracts (4,023) (9,507)
Interest rate swaps (23,799) (3,121)
Total liabilities, at fair value: (27,822) (12,628)
Level 2 | Debt Investments    
Assets, at fair value:    
Fair value 1,276,609 1,750,395
Level 2 | Equity Investments    
Assets, at fair value:    
Fair value 0 0
Level 3    
Assets, at fair value:    
Fair value 8,339,916 6,804,856
Money market funds 0 0
Forward currency contracts 0 0
Interest rate swaps 0 0
Total assets, at fair value: 8,339,916 6,804,856
Liabilities, at fair value:    
Forward currency contracts 0 0
Interest rate swaps 0 0
Total liabilities, at fair value: 0 0
Level 3 | Debt Investments    
Assets, at fair value:    
Fair value 8,240,249 6,740,019
Level 3 | Equity Investments    
Assets, at fair value:    
Fair value $ 99,667 $ 64,837
[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.