v3.26.1
Investments - Schedule of Portfolio Composition by Industry at Amortization Cost and Fair Value (Details) - USD ($)
$ in Thousands
9 Months Ended 12 Months Ended
Jun. 30, 2026
Sep. 30, 2025
Schedule of Investments [Line Items]    
Amortized Cost $ 9,727,658 $ 8,479,341
Fair Value $ 9,616,525 [1] $ 8,555,251 [2]
Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Aerospace & Defense    
Schedule of Investments [Line Items]    
Amortized Cost $ 160,771 $ 120,841
Fair Value $ 158,632 $ 121,150
Aerospace & Defense | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.60% 1.40%
Aerospace & Defense | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.60% 1.40%
Air Freight & Logistics    
Schedule of Investments [Line Items]    
Amortized Cost $ 105,656 $ 105,489
Fair Value $ 106,377 $ 106,153
Air Freight & Logistics | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.10% 1.20%
Air Freight & Logistics | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.10% 1.20%
Airlines    
Schedule of Investments [Line Items]    
Amortized Cost $ 5,989 $ 20,374
Fair Value $ 5,994 $ 20,423
Airlines | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.20%
Airlines | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.20%
Auto Components    
Schedule of Investments [Line Items]    
Amortized Cost $ 103,123 $ 111,710
Fair Value $ 100,827 $ 111,841
Auto Components | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.10% 1.30%
Auto Components | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.10% 1.30%
Automobiles    
Schedule of Investments [Line Items]    
Amortized Cost $ 292,115 $ 268,537
Fair Value $ 292,020 $ 271,584
Automobiles | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.00% 3.20%
Automobiles | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.00% 3.20%
Banks    
Schedule of Investments [Line Items]    
Amortized Cost $ 22,550 $ 16,055
Fair Value $ 22,017 $ 16,215
Banks | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Banks | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Beverages    
Schedule of Investments [Line Items]    
Amortized Cost $ 82,057 $ 81,503
Fair Value $ 80,319 $ 81,036
Beverages | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.80% 1.00%
Beverages | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.80% 0.90%
Building Products    
Schedule of Investments [Line Items]    
Amortized Cost $ 2,086 $ 3,266
Fair Value $ 2,094 $ 3,334
Building Products | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Building Products | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Capital Markets    
Schedule of Investments [Line Items]    
Amortized Cost $ 60,403 $ 66,357
Fair Value $ 60,193 $ 66,686
Capital Markets | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.80%
Capital Markets | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.80%
Chemicals    
Schedule of Investments [Line Items]    
Amortized Cost $ 126,356 $ 143,213
Fair Value $ 126,230 $ 143,537
Chemicals | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.30% 1.70%
Chemicals | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.30% 1.70%
Commercial Services & Supplies    
Schedule of Investments [Line Items]    
Amortized Cost $ 257,998 $ 156,518
Fair Value $ 257,658 $ 157,756
Commercial Services & Supplies | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 2.60% 1.80%
Commercial Services & Supplies | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 2.70% 1.80%
Construction & Engineering    
Schedule of Investments [Line Items]    
Amortized Cost $ 55,965 $ 89,637
Fair Value $ 55,596 $ 90,248
Construction & Engineering | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 1.10%
Construction & Engineering | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 1.00%
Construction Materials    
Schedule of Investments [Line Items]    
Amortized Cost $ 16,939 $ 17,046
Fair Value $ 17,104 $ 17,103
Construction Materials | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Construction Materials | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Consumer Finance    
Schedule of Investments [Line Items]    
Amortized Cost $ 25,971 $ 26,096
Fair Value $ 25,475 $ 26,116
Consumer Finance | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.30% 0.30%
Consumer Finance | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.30% 0.30%
Containers & Packaging    
Schedule of Investments [Line Items]    
Amortized Cost $ 122,668 $ 111,902
Fair Value $ 119,253 $ 112,592
Containers & Packaging | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.30% 1.30%
Containers & Packaging | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.20% 1.30%
Diversified Consumer Services    
Schedule of Investments [Line Items]    
Amortized Cost $ 506,728 $ 379,377
Fair Value $ 494,694 $ 376,480
Diversified Consumer Services | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 5.20% 4.50%
Diversified Consumer Services | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 5.10% 4.40%
Diversified Financial Services    
Schedule of Investments [Line Items]    
Amortized Cost $ 505,489 $ 506,912
Fair Value $ 501,535 $ 513,068
Diversified Financial Services | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 5.20% 6.00%
Diversified Financial Services | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 5.20% 6.00%
Electric Utilities    
Schedule of Investments [Line Items]    
Amortized Cost $ 6,644 $ 6,440
Fair Value $ 6,807 $ 6,525
Electric Utilities | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Electric Utilities | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Electrical Equipment    
Schedule of Investments [Line Items]    
Amortized Cost $ 0 $ 25,413
Fair Value $ 0 $ 25,764
Electrical Equipment | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.00% 0.30%
Electrical Equipment | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.00% 0.30%
Food & Staples Retailing    
Schedule of Investments [Line Items]    
Amortized Cost $ 17,046 $ 13,666
Fair Value $ 16,882 $ 13,746
Food & Staples Retailing | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Food & Staples Retailing | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Food Products    
Schedule of Investments [Line Items]    
Amortized Cost $ 124,487 $ 129,183
Fair Value $ 125,326 $ 130,252
Food Products | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.30% 1.50%
Food Products | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.30% 1.50%
Healthcare Equipment & Supplies    
Schedule of Investments [Line Items]    
Amortized Cost $ 642,853 $ 365,741
Fair Value $ 644,929 $ 369,814
Healthcare Equipment & Supplies | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 6.60% 4.30%
Healthcare Equipment & Supplies | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 6.70% 4.30%
Healthcare Providers & Services    
Schedule of Investments [Line Items]    
Amortized Cost $ 530,360 $ 531,512
Fair Value $ 528,214 $ 535,199
Healthcare Providers & Services | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 5.40% 6.30%
Healthcare Providers & Services | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 5.50% 6.30%
Healthcare Technology    
Schedule of Investments [Line Items]    
Amortized Cost $ 685,968 $ 463,153
Fair Value $ 681,988 $ 467,734
Healthcare Technology | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 7.10% 5.50%
Healthcare Technology | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 7.10% 5.50%
Hotels, Restaurants & Leisure    
Schedule of Investments [Line Items]    
Amortized Cost $ 676,238 $ 576,856
Fair Value $ 680,585 $ 581,461
Hotels, Restaurants & Leisure | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 7.00% 6.80%
Hotels, Restaurants & Leisure | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 7.10% 6.80%
Household Durables    
Schedule of Investments [Line Items]    
Amortized Cost $ 13,256 $ 12,994
Fair Value $ 13,222 $ 12,986
Household Durables | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Household Durables | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.20%
Household Products    
Schedule of Investments [Line Items]    
Amortized Cost $ 21,305 $ 21,453
Fair Value $ 21,134 $ 21,573
Household Products | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Household Products | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.30%
Industrial Conglomerates    
Schedule of Investments [Line Items]    
Amortized Cost $ 92,213 $ 92,567
Fair Value $ 89,853 $ 93,342
Industrial Conglomerates | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.90% 1.10%
Industrial Conglomerates | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.90% 1.10%
Insurance    
Schedule of Investments [Line Items]    
Amortized Cost $ 613,842 $ 490,870
Fair Value $ 606,766 $ 496,022
Insurance | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 6.30% 5.80%
Insurance | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 6.30% 5.80%
IT Services    
Schedule of Investments [Line Items]    
Amortized Cost $ 307,721 $ 358,874
Fair Value $ 299,986 $ 360,665
IT Services | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.20% 4.20%
IT Services | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.10% 4.20%
Leisure Products    
Schedule of Investments [Line Items]    
Amortized Cost $ 47,265 $ 50,301
Fair Value $ 44,060 $ 49,611
Leisure Products | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.50% 0.60%
Leisure Products | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.50% 0.60%
Life Sciences Tools & Services    
Schedule of Investments [Line Items]    
Amortized Cost $ 57,115 $ 56,286
Fair Value $ 56,141 $ 56,306
Life Sciences Tools & Services | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Life Sciences Tools & Services | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Machinery    
Schedule of Investments [Line Items]    
Amortized Cost $ 54,340 $ 61,988
Fair Value $ 53,971 $ 62,202
Machinery | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Machinery | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Media    
Schedule of Investments [Line Items]    
Amortized Cost $ 63,521 $ 63,456
Fair Value $ 62,581 $ 63,094
Media | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Media | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.70% 0.70%
Oil, Gas & Consumable Fuels    
Schedule of Investments [Line Items]    
Amortized Cost $ 8,053 $ 19,054
Fair Value $ 8,038 $ 19,194
Oil, Gas & Consumable Fuels | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.20%
Oil, Gas & Consumable Fuels | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.20%
Paper & Forest Products    
Schedule of Investments [Line Items]    
Amortized Cost $ 5,920 $ 5,966
Fair Value $ 5,910 $ 5,985
Paper & Forest Products | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Paper & Forest Products | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Personal Products    
Schedule of Investments [Line Items]    
Amortized Cost $ 8,995 $ 12,000
Fair Value $ 8,983 $ 12,014
Personal Products | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Personal Products | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Pharmaceuticals    
Schedule of Investments [Line Items]    
Amortized Cost $ 115,163 $ 109,522
Fair Value $ 115,190 $ 111,458
Pharmaceuticals | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.20% 1.30%
Pharmaceuticals | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 1.20% 1.30%
Professional Services    
Schedule of Investments [Line Items]    
Amortized Cost $ 379,316 $ 354,344
Fair Value $ 369,930 $ 354,331
Professional Services | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.90% 4.20%
Professional Services | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.80% 4.10%
Real Estate Management & Development    
Schedule of Investments [Line Items]    
Amortized Cost $ 4,865 $ 4,899
Fair Value $ 4,566 $ 4,904
Real Estate Management & Development | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.00% 0.10%
Real Estate Management & Development | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.00% 0.10%
Road & Rail    
Schedule of Investments [Line Items]    
Amortized Cost $ 35,769 $ 98,457
Fair Value $ 35,754 $ 98,694
Road & Rail | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.40% 1.20%
Road & Rail | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.40% 1.20%
Software    
Schedule of Investments [Line Items]    
Amortized Cost $ 2,067,335 $ 1,694,514
Fair Value $ 2,020,709 $ 1,729,397
Software | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 21.20% 20.00%
Software | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 21.00% 20.20%
Specialized Finance    
Schedule of Investments [Line Items]    
Amortized Cost $ 226,923 $ 161,487
Fair Value $ 224,585 $ 162,943
Specialized Finance | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 2.30% 1.90%
Specialized Finance | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 2.30% 1.90%
Specialty Retail    
Schedule of Investments [Line Items]    
Amortized Cost $ 354,787 $ 357,631
Fair Value $ 352,079 $ 360,091
Specialty Retail | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.60% 4.20%
Specialty Retail | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 3.70% 4.20%
Trading Companies & Distributors    
Schedule of Investments [Line Items]    
Amortized Cost $ 17,041 $ 16,494
Fair Value $ 16,154 $ 15,336
Trading Companies & Distributors | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Trading Companies & Distributors | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Transportation Infrastructure    
Schedule of Investments [Line Items]    
Amortized Cost $ 66,496 $ 68,858
Fair Value $ 66,178 $ 68,507
Transportation Infrastructure | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.70% 0.80%
Transportation Infrastructure | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.70% 0.80%
Water Utilities    
Schedule of Investments [Line Items]    
Amortized Cost $ 29,957 $ 30,529
Fair Value $ 29,986 $ 30,779
Water Utilities | Investments, at Amortized Cost | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.30% 0.40%
Water Utilities | Investments, at Fair Value | Industry Concentration Risk    
Schedule of Investments [Line Items]    
Concentration risk, percentage 0.30% 0.40%
[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.