v3.25.2
Portfolio Investments - Schedule of Portfolio Composition (Details) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Jun. 30, 2025
Sep. 30, 2024
Schedule of Investments [Line Items]    
Investment owned, at cost $ 6,315,137 [1] $ 4,530,412 [2]
Total investments at fair value $ 6,362,926 [1] $ 4,576,233 [2]
% of Net Assets 150.90% 144.62% [2]
United States    
Schedule of Investments [Line Items]    
Investment owned, at cost $ 5,345,058 $ 3,845,172
Total investments at fair value 5,343,508 3,870,681
United Kingdom    
Schedule of Investments [Line Items]    
Investment owned, at cost 353,844 273,693
Total investments at fair value 373,106 285,463
Germany    
Schedule of Investments [Line Items]    
Investment owned, at cost 176,616 0
Total investments at fair value 186,629 0
Sweden    
Schedule of Investments [Line Items]    
Investment owned, at cost 175,706 55,033
Total investments at fair value 182,784 55,211
Netherlands    
Schedule of Investments [Line Items]    
Investment owned, at cost 110,586 51,988
Total investments at fair value 116,102 53,686
Canada    
Schedule of Investments [Line Items]    
Investment owned, at cost 66,634 66,649
Total investments at fair value 68,856 69,066
Luxembourg    
Schedule of Investments [Line Items]    
Investment owned, at cost 50,670 87,862
Total investments at fair value 55,493 89,270
Costa Rica    
Schedule of Investments [Line Items]    
Investment owned, at cost 14,857 13,174
Total investments at fair value 14,992 13,269
Switzerland    
Schedule of Investments [Line Items]    
Investment owned, at cost 10,366 10,309
Total investments at fair value 10,280 10,199
Chile    
Schedule of Investments [Line Items]    
Investment owned, at cost 7,775 11,285
Total investments at fair value 7,940 12,093
Australia    
Schedule of Investments [Line Items]    
Investment owned, at cost 1,771 2,030
Total investments at fair value 1,818 2,027
France    
Schedule of Investments [Line Items]    
Investment owned, at cost 1,254 12,907
Total investments at fair value 1,418 13,702
Cayman Islands    
Schedule of Investments [Line Items]    
Investment owned, at cost 0 60,841
Total investments at fair value 0 61,815
India    
Schedule of Investments [Line Items]    
Investment owned, at cost 0 39,469
Total investments at fair value $ 0 $ 39,751
Investment Owned, At Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 100.00% 100.00%
Investment Owned, At Cost | Geographic Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 100.00% 100.00%
Investment Owned, At Cost | Geographic Concentration Risk | United States    
Schedule of Investments [Line Items]    
% of Total Investments 84.64% 84.89%
Investment Owned, At Cost | Geographic Concentration Risk | United Kingdom    
Schedule of Investments [Line Items]    
% of Total Investments 5.60% 6.04%
Investment Owned, At Cost | Geographic Concentration Risk | Germany    
Schedule of Investments [Line Items]    
% of Total Investments 2.80% 0.00%
Investment Owned, At Cost | Geographic Concentration Risk | Sweden    
Schedule of Investments [Line Items]    
% of Total Investments 2.78% 1.21%
Investment Owned, At Cost | Geographic Concentration Risk | Netherlands    
Schedule of Investments [Line Items]    
% of Total Investments 1.75% 1.15%
Investment Owned, At Cost | Geographic Concentration Risk | Canada    
Schedule of Investments [Line Items]    
% of Total Investments 1.06% 1.47%
Investment Owned, At Cost | Geographic Concentration Risk | Luxembourg    
Schedule of Investments [Line Items]    
% of Total Investments 0.80% 1.94%
Investment Owned, At Cost | Geographic Concentration Risk | Costa Rica    
Schedule of Investments [Line Items]    
% of Total Investments 0.24% 0.29%
Investment Owned, At Cost | Geographic Concentration Risk | Switzerland    
Schedule of Investments [Line Items]    
% of Total Investments 0.16% 0.23%
Investment Owned, At Cost | Geographic Concentration Risk | Chile    
Schedule of Investments [Line Items]    
% of Total Investments 0.12% 0.25%
Investment Owned, At Cost | Geographic Concentration Risk | Australia    
Schedule of Investments [Line Items]    
% of Total Investments 0.03% 0.04%
Investment Owned, At Cost | Geographic Concentration Risk | France    
Schedule of Investments [Line Items]    
% of Total Investments 0.02% 0.28%
Investment Owned, At Cost | Geographic Concentration Risk | Cayman Islands    
Schedule of Investments [Line Items]    
% of Total Investments 0.00% 1.34%
Investment Owned, At Cost | Geographic Concentration Risk | India    
Schedule of Investments [Line Items]    
% of Total Investments 0.00% 0.87%
Investment Owned, At Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 100.00% 100.00%
Investment Owned, At Fair Value | Geographic Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 100.00% 100.00%
% of Net Assets 150.90% 144.62%
Investment Owned, At Fair Value | Geographic Concentration Risk | United States    
Schedule of Investments [Line Items]    
% of Total Investments 84.00% 84.59%
% of Net Assets 126.73% 122.34%
Investment Owned, At Fair Value | Geographic Concentration Risk | United Kingdom    
Schedule of Investments [Line Items]    
% of Total Investments 5.86% 6.24%
% of Net Assets 8.85% 9.02%
Investment Owned, At Fair Value | Geographic Concentration Risk | Germany    
Schedule of Investments [Line Items]    
% of Total Investments 2.93% 0.00%
% of Net Assets 4.43% 0.00%
Investment Owned, At Fair Value | Geographic Concentration Risk | Sweden    
Schedule of Investments [Line Items]    
% of Total Investments 2.87% 1.21%
% of Net Assets 4.33% 1.74%
Investment Owned, At Fair Value | Geographic Concentration Risk | Netherlands    
Schedule of Investments [Line Items]    
% of Total Investments 1.82% 1.17%
% of Net Assets 2.75% 1.70%
Investment Owned, At Fair Value | Geographic Concentration Risk | Canada    
Schedule of Investments [Line Items]    
% of Total Investments 1.08% 1.51%
% of Net Assets 1.63% 2.18%
Investment Owned, At Fair Value | Geographic Concentration Risk | Luxembourg    
Schedule of Investments [Line Items]    
% of Total Investments 0.87% 1.95%
% of Net Assets 1.32% 2.82%
Investment Owned, At Fair Value | Geographic Concentration Risk | Costa Rica    
Schedule of Investments [Line Items]    
% of Total Investments 0.24% 0.29%
% of Net Assets 0.36% 0.42%
Investment Owned, At Fair Value | Geographic Concentration Risk | Switzerland    
Schedule of Investments [Line Items]    
% of Total Investments 0.16% 0.22%
% of Net Assets 0.24% 0.32%
Investment Owned, At Fair Value | Geographic Concentration Risk | Chile    
Schedule of Investments [Line Items]    
% of Total Investments 0.12% 0.26%
% of Net Assets 0.19% 0.38%
Investment Owned, At Fair Value | Geographic Concentration Risk | Australia    
Schedule of Investments [Line Items]    
% of Total Investments 0.03% 0.04%
% of Net Assets 0.04% 0.06%
Investment Owned, At Fair Value | Geographic Concentration Risk | France    
Schedule of Investments [Line Items]    
% of Total Investments 0.02% 0.30%
% of Net Assets 0.03% 0.43%
Investment Owned, At Fair Value | Geographic Concentration Risk | Cayman Islands    
Schedule of Investments [Line Items]    
% of Total Investments 0.00% 1.35%
% of Net Assets 0.00% 1.95%
Investment Owned, At Fair Value | Geographic Concentration Risk | India    
Schedule of Investments [Line Items]    
% of Total Investments 0.00% 0.87%
% of Net Assets 0.00% 1.26%
Senior Secured Debt    
Schedule of Investments [Line Items]    
Investment owned, at cost $ 5,706,997 $ 4,037,376
Total investments at fair value $ 5,744,828 $ 4,073,936
% of Net Assets 136.24% 128.74%
Senior Secured Debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 90.37% 89.12%
Senior Secured Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 90.29% 89.02%
Subordinated Debt    
Schedule of Investments [Line Items]    
Investment owned, at cost $ 582,374 $ 468,071
Total investments at fair value $ 586,059 $ 476,093
% of Net Assets 13.90% 15.05%
Subordinated Debt | Investment Owned, At Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 9.22% 10.33%
Subordinated Debt | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 9.21% 10.40%
Preferred Equity    
Schedule of Investments [Line Items]    
Investment owned, at cost $ 13,945 $ 12,234
Total investments at fair value $ 18,731 $ 14,008
% of Net Assets 0.44% 0.44%
Preferred Equity | Investment Owned, At Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 0.22% 0.27%
Preferred Equity | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 0.29% 0.31%
Common Equity and Warrants    
Schedule of Investments [Line Items]    
Investment owned, at cost $ 11,821 $ 12,731
Total investments at fair value $ 13,308 $ 12,196
% of Net Assets 0.32% 0.39%
Common Equity and Warrants | Investment Owned, At Cost | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 0.19% 0.28%
Common Equity and Warrants | Investment Owned, At Fair Value | Investment Type Concentration Risk    
Schedule of Investments [Line Items]    
% of Total Investments 0.21% 0.27%
[1] Non-Control/Non-Affiliate Investments are investments that are neither Control Investments nor Affiliate Investments. Control Investments generally are defined by the Investment Company Act of 1940, as amended (the “Investment Company Act”), as investments in companies in which the Company owns more than 25% of the voting securities and/or has the power to exercise control over the management or policies of the company. Affiliate Investments generally are defined by the Investment Company Act as investments in companies in which the Company owns between 5% and 25% of the voting securities.
[2] Non-Control/Non-Affiliate Investments are investments that are neither Control Investments nor Affiliate Investments. Control Investments generally are defined by the Investment Company Act, as investments in companies in which the Company owns more than 25% of the voting securities and/or has the power to exercise control over the management or policies of the company. Affiliate Investments generally are defined by the Investment Company Act as investments in companies in which the Company owns between 5% and 25% of the voting securities.