Portfolio Investments - Composition of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Sep. 30, 2023
Schedule of Investments [Line Items]
Fair Value	$ 4,172,105	$ 1,915,597
% of Debt Investments	100.00%	100.00%
Floating rate
Schedule of Investments [Line Items]
Fair Value	$ 3,811,074	$ 1,716,908
% of Debt Investments	91.35%	89.63%
Fixed rate
Schedule of Investments [Line Items]
Fair Value	$ 361,031	$ 198,689
% of Debt Investments	8.65%	10.37%