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Investments - Schedule of Portfolio Composition by Industry at Amortization Cost and Fair Value (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 5,569,604 $ 4,895,397
Investments, at fair value $ 5,446,356 [1] $ 4,894,886 [2]
Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 100.00% 100.00%
Aerospace and Defense    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 65,825 $ 114,075
Investments, at fair value $ 64,365 $ 112,636
Aerospace and Defense | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.20% 2.30%
Aerospace and Defense | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.20% 2.30%
Airlines    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 961 $ 967
Investments, at fair value $ 926 $ 936
Airlines | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Airlines | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Auto Components    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 41,487 $ 32,334
Investments, at fair value $ 41,026 $ 32,566
Auto Components | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.70% 0.70%
Auto Components | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 0.70%
Automobiles    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 262,821 $ 139,501
Investments, at fair value $ 260,506 $ 140,499
Automobiles | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.70% 2.90%
Automobiles | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.80% 2.90%
Beverages    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 59,650 $ 61,557
Investments, at fair value $ 57,804 $ 60,868
Beverages | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.10% 1.30%
Beverages | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.10% 1.20%
Biotechnology    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 1,769 $ 23,968
Investments, at fair value $ 1,536 $ 25,439
Biotechnology | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.50%
Biotechnology | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.50%
Building Products    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 17,764 $ 9,395
Investments, at fair value $ 17,770 $ 11,243
Building Products | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.30% 0.20%
Building Products | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.30% 0.20%
Chemicals    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 87,657 $ 64,363
Investments, at fair value $ 79,461 $ 64,262
Chemicals | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.60% 1.30%
Chemicals | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.50% 1.30%
Commercial Services and Supplies    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 137,435 $ 98,529
Investments, at fair value $ 135,584 $ 99,595
Commercial Services and Supplies | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 2.00%
Commercial Services and Supplies | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 2.00%
Communications Equipment    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 11,414 $ 11,382
Investments, at fair value $ 11,162 $ 11,347
Communications Equipment | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Communications Equipment | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Construction & Engineering    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 0 $ 49,060
Investments, at fair value $ 0 $ 49,166
Construction & Engineering | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 1.00%
Construction & Engineering | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 1.00%
Consumer Finance    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 0 $ 2,057
Investments, at fair value $ 0 $ 2,627
Consumer Finance | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Consumer Finance | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.10%
Containers and Packaging    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 44,094 $ 10,407
Investments, at fair value $ 44,198 $ 10,545
Containers and Packaging | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 0.20%
Containers and Packaging | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 0.20%
Distributors    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 5,942 $ 6,189
Investments, at fair value $ 5,941 $ 6,089
Distributors | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Distributors | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Diversified Consumer Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 241,453 $ 138,358
Investments, at fair value $ 236,896 $ 134,232
Diversified Consumer Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.30% 2.80%
Diversified Consumer Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.30% 2.70%
Diversified Financial Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 27,160 $ 16,345
Investments, at fair value $ 26,928 $ 16,497
Diversified Financial Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.50% 0.30%
Diversified Financial Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.50% 0.30%
Diversified Telecommunication Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 1,609 $ 1,616
Investments, at fair value $ 1,628 $ 1,645
Diversified Telecommunication Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Diversified Telecommunication Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Electronic Equipment, Instruments and Components    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 137,087 $ 124,995
Investments, at fair value $ 138,011 $ 125,481
Electronic Equipment, Instruments and Components | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 2.60%
Electronic Equipment, Instruments and Components | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 2.60%
Energy Equipment and Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 4,700 $ 4,388
Investments, at fair value $ 1,740 $ 2,399
Energy Equipment and Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Energy Equipment and Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.00% 0.00%
Food and Staples Retailing    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 83,134 $ 124,003
Investments, at fair value $ 84,744 $ 128,574
Food and Staples Retailing | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.50% 2.50%
Food and Staples Retailing | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.60% 2.60%
Food Products    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 135,841 $ 112,773
Investments, at fair value $ 136,802 $ 119,568
Food Products | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.40% 2.30%
Food Products | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 2.40%
Healthcare Equipment and Supplies    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 141,925 $ 162,211
Investments, at fair value $ 131,962 $ 157,959
Healthcare Equipment and Supplies | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 3.30%
Healthcare Equipment and Supplies | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.40% 3.20%
Healthcare Providers and Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 492,321 $ 552,202
Investments, at fair value $ 444,736 $ 532,463
Healthcare Providers and Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 8.80% 11.30%
Healthcare Providers and Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 8.20% 10.90%
Health Care Technology    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 197,946 $ 147,269
Investments, at fair value $ 200,658 $ 150,565
Health Care Technology | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 3.60% 3.00%
Health Care Technology | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 3.70% 3.10%
Hotels, Restaurants and Leisure    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 132,351 $ 174,667
Investments, at fair value $ 134,159 $ 172,285
Hotels, Restaurants and Leisure | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.40% 3.60%
Hotels, Restaurants and Leisure | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.50% 3.50%
Household Durables    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 8,897 $ 5,338
Investments, at fair value $ 9,275 $ 5,694
Household Durables | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.10%
Household Durables | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.10%
Household Products    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 5,473 $ 5,199
Investments, at fair value $ 5,265 $ 5,140
Household Products | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Household Products | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Industrial Conglomerates    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 31,560 $ 18,403
Investments, at fair value $ 30,407 $ 18,560
Industrial Conglomerates | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.40%
Industrial Conglomerates | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.40%
Insurance    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 232,074 $ 232,137
Investments, at fair value $ 226,158 $ 234,529
Insurance | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.20% 4.70%
Insurance | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.20% 4.80%
Internet and Catalog Retail    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 61,193 $ 30,836
Investments, at fair value $ 61,299 $ 31,127
Internet and Catalog Retail | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.10% 0.60%
Internet and Catalog Retail | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.10% 0.60%
IT Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 264,343 $ 298,383
Investments, at fair value $ 249,240 $ 302,487
IT Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.80% 6.10%
IT Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 4.60% 6.20%
Leisure Products    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 11,797 $ 11,869
Investments, at fair value $ 13,478 $ 12,575
Leisure Products | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Leisure Products | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.30%
Life Sciences Tools & Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 50,125 $ 56,285
Investments, at fair value $ 49,478 $ 57,004
Life Sciences Tools & Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.90% 1.10%
Life Sciences Tools & Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.90% 1.20%
Machinery    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 34,594 $ 32,374
Investments, at fair value $ 31,750 $ 29,377
Machinery | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Machinery | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.60%
Marine    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 18,813 $ 16,729
Investments, at fair value $ 18,399 $ 16,877
Marine | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.30% 0.30%
Marine | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.30% 0.30%
Media    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 6,396 $ 5,295
Investments, at fair value $ 6,503 $ 5,397
Media | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Media | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.10% 0.10%
Multiline Retail    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 45,090 $ 46,382
Investments, at fair value $ 45,138 $ 46,470
Multiline Retail | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 1.00%
Multiline Retail | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 1.00%
Oil, Gas and Consumable Fuels    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 92,234 $ 92,993
Investments, at fair value $ 90,054 $ 92,720
Oil, Gas and Consumable Fuels | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.70% 1.90%
Oil, Gas and Consumable Fuels | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 1.70% 1.90%
Paper and Forest Products    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 10,579 $ 8,970
Investments, at fair value $ 10,640 $ 8,921
Paper and Forest Products | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Paper and Forest Products | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.20% 0.20%
Personal Products    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 36,654 $ 37,019
Investments, at fair value $ 33,869 $ 33,727
Personal Products | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.70% 0.80%
Personal Products | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.70%
Pharmaceuticals    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 154,608 $ 106,859
Investments, at fair value $ 150,263 $ 108,458
Pharmaceuticals | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.80% 2.20%
Pharmaceuticals | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.80% 2.20%
Professional Services    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 116,650 $ 104,427
Investments, at fair value $ 116,622 $ 106,898
Professional Services | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.10% 2.10%
Professional Services | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.10% 2.20%
Real Estate Management and Development    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 123,697 $ 97,205
Investments, at fair value $ 119,120 $ 96,066
Real Estate Management and Development | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.20% 2.00%
Real Estate Management and Development | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 2.20% 2.00%
Road and Rail    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 35,801 $ 37,012
Investments, at fair value $ 35,742 $ 36,751
Road and Rail | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.80%
Road and Rail | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.70% 0.80%
Software    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 1,410,563 $ 1,077,321
Investments, at fair value $ 1,401,424 $ 1,084,864
Software | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 25.30% 22.00%
Software | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 25.70% 22.20%
Specialty Retail    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 365,734 $ 286,417
Investments, at fair value $ 367,521 $ 292,446
Specialty Retail | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 6.60% 5.90%
Specialty Retail | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 6.70% 6.00%
Technology Hardware, Storage and Peripherals    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 23,269 $ 23,815
Investments, at fair value $ 22,852 $ 23,717
Technology Hardware, Storage and Peripherals | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.40% 0.50%
Technology Hardware, Storage and Peripherals | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.40% 0.50%
Textiles, Apparel and Luxury Goods    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 44,882 $ 45,092
Investments, at fair value $ 42,302 $ 38,627
Textiles, Apparel and Luxury Goods | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 0.90%
Textiles, Apparel and Luxury Goods | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.80% 0.80%
Trading Companies and Distributors    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 34,410 $ 18,936
Investments, at fair value $ 33,597 $ 19,311
Trading Companies and Distributors | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.40%
Trading Companies and Distributors | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.60% 0.40%
Water Utilities    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Amortized Cost $ 17,822 $ 17,490
Investments, at fair value $ 17,417 $ 17,657
Water Utilities | Investments, at Amortized Cost | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.30% 0.40%
Water Utilities | Investments, At Fair Value | Industry Concentration Risk    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Concentration risk, percentage 0.30% 0.40%
[1] The fair values of investments were valued using significant unobservable inputs, unless noted otherwise. See Note 6. Fair Value Measurements.
[2] The fair values of substantially all investments were valued using significant unobservable inputs. See Note 6. Fair Value Measurements.