Investments - Schedules of Portfolio Composition by Geographic Region 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 |
$ 2,674,753
|
|
$ 2,176,447
|
|
| Fair Value |
$ 2,667,489
|
[1] |
$ 2,209,174
|
[2] |
| Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
100.00%
|
|
100.00%
|
|
| Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
100.00%
|
|
100.00%
|
|
| Southeast |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 485,350
|
|
$ 445,901
|
|
| Fair Value |
$ 484,477
|
|
$ 449,900
|
|
| Southeast | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
18.20%
|
|
20.50%
|
|
| Southeast | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
18.20%
|
|
20.40%
|
|
| Midwest |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 473,431
|
|
$ 395,386
|
|
| Fair Value |
$ 473,127
|
|
$ 401,851
|
|
| Midwest | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
17.70%
|
|
18.20%
|
|
| Midwest | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
17.70%
|
|
18.20%
|
|
| Mid-Atlantic |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 434,279
|
|
$ 285,602
|
|
| Fair Value |
$ 433,386
|
|
$ 288,569
|
|
| Mid-Atlantic | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
16.30%
|
|
13.10%
|
|
| Mid-Atlantic | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
16.20%
|
|
13.10%
|
|
| West |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 404,742
|
|
$ 369,906
|
|
| Fair Value |
$ 403,920
|
|
$ 374,368
|
|
| West | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
15.10%
|
|
17.00%
|
|
| West | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
15.10%
|
|
16.90%
|
|
| Southwest |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 369,607
|
|
$ 255,497
|
|
| Fair Value |
$ 367,868
|
|
$ 258,152
|
|
| Southwest | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
13.80%
|
|
11.70%
|
|
| Southwest | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
13.80%
|
|
11.70%
|
|
| Northeast |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 166,438
|
|
$ 144,153
|
|
| Fair Value |
$ 163,430
|
|
$ 145,343
|
|
| Northeast | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
6.20%
|
|
6.60%
|
|
| Northeast | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
6.10%
|
|
6.60%
|
|
| United Kingdom |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 188,045
|
|
$ 140,614
|
|
| Fair Value |
$ 186,832
|
|
$ 143,807
|
|
| United Kingdom | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
7.00%
|
|
6.50%
|
|
| United Kingdom | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
7.00%
|
|
6.50%
|
|
| Germany |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 45,892
|
|
$ 53,904
|
|
| Fair Value |
$ 47,038
|
|
$ 58,632
|
|
| Germany | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
1.70%
|
|
2.50%
|
|
| Germany | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
1.80%
|
|
2.70%
|
|
| Canada |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 32,188
|
|
$ 20,172
|
|
| Fair Value |
$ 31,156
|
|
$ 20,437
|
|
| Canada | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
1.20%
|
|
0.90%
|
|
| Canada | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
1.20%
|
|
0.90%
|
|
| Australia |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 27,211
|
|
$ 25,160
|
|
| Fair Value |
$ 28,360
|
|
$ 25,855
|
|
| Australia | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
1.00%
|
|
1.20%
|
|
| Australia | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
1.10%
|
|
1.20%
|
|
| Jersey |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 20,451
|
|
$ 20,433
|
|
| Fair Value |
$ 20,530
|
|
$ 21,123
|
|
| Jersey | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.80%
|
|
1.00%
|
|
| Jersey | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.80%
|
|
1.00%
|
|
| Finland |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 8,118
|
|
$ 6,987
|
|
| Fair Value |
$ 8,166
|
|
$ 7,561
|
|
| Finland | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.30%
|
|
0.30%
|
|
| Finland | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.30%
|
|
0.30%
|
|
| Netherlands |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 5,668
|
|
$ 4,250
|
|
| Fair Value |
$ 5,786
|
|
$ 4,621
|
|
| Netherlands | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.20%
|
|
0.20%
|
|
| Netherlands | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.20%
|
|
0.20%
|
|
| Sweden |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 5,364
|
|
$ 5,264
|
|
| Fair Value |
$ 5,394
|
|
$ 5,459
|
|
| Sweden | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.20%
|
|
0.20%
|
|
| Sweden | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.20%
|
|
0.20%
|
|
| France |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 5,138
|
|
$ 2,281
|
|
| Fair Value |
$ 5,134
|
|
$ 2,497
|
|
| France | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.20%
|
|
0.10%
|
|
| France | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.20%
|
|
0.10%
|
|
| Israel |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 1,963
|
|
$ 81
|
|
| Fair Value |
$ 2,055
|
|
$ 123
|
|
| Israel | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.10%
|
|
0.00%
|
|
| Israel | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.10%
|
|
0.00%
|
|
| Denmark |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 546
|
|
$ 544
|
|
| Fair Value |
$ 538
|
|
$ 545
|
|
| Denmark | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.00%
|
|
0.00%
|
|
| Denmark | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.00%
|
|
0.00%
|
|
| Luxembourg |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Amortized Cost |
$ 322
|
|
$ 312
|
|
| Fair Value |
$ 292
|
|
$ 331
|
|
| Luxembourg | Investments, at Amortized Cost | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.00%
|
|
0.00%
|
|
| Luxembourg | Investments, at Fair Value | Geographic Concentration Risk |
|
|
|
|
| Schedule of Investments [Line Items] |
|
|
|
|
| Concentration risk, percentage |
0.00%
|
|
0.00%
|
|
|
|