Share Data and Net Assets - Schedule of Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Sep. 29, 2023 |
Jun. 30, 2023 |
Mar. 31, 2023 |
Dec. 30, 2022 |
Sep. 30, 2022 |
Jun. 30, 2022 |
Mar. 31, 2022 |
Dec. 31, 2021 |
Sep. 30, 2021 |
Jun. 30, 2021 |
Mar. 31, 2021 |
Dec. 31, 2020 |
Sep. 30, 2023 |
Sep. 30, 2022 |
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2019 |
|
| Investment Company, Changes in Net Assets [Line Items] | |||||||||||||||||
| Amount per share (in dollars per share) | $ 2.61 | $ 1.95 | $ 1.515 | $ 1.17 | $ 1.14 | ||||||||||||
| Distributions to stockholders | $ 180,000 | $ 115,300 | $ 79,800 | ||||||||||||||
| Issuance of common stock under dividend reinvestment plan (shares) | 297,336 | 165,651 | 112,573 | ||||||||||||||
| Issuance of common stock under dividend reinvestment plan | $ 5,854 | $ 3,409 | $ 2,170 | ||||||||||||||
| Quarterly | |||||||||||||||||
| Investment Company, Changes in Net Assets [Line Items] | |||||||||||||||||
| Amount per share (in dollars per share) | $ 0.55 | $ 0.55 | $ 0.55 | $ 0.54 | $ 0.51 | $ 0.495 | $ 0.48 | $ 0.465 | $ 0.435 | $ 0.39 | $ 0.36 | $ 0.33 | |||||
| Distributions to stockholders | $ 40,900 | $ 41,300 | $ 41,100 | $ 32,000 | $ 30,200 | $ 29,400 | $ 28,500 | $ 27,200 | $ 25,500 | $ 22,900 | $ 16,400 | $ 15,000 | |||||
| Issuance of common stock under dividend reinvestment plan (shares) | 76,766 | 57,279 | 68,412 | 53,369 | 51,181 | 43,676 | 34,804 | 35,990 | 28,358 | 25,660 | 27,234 | 31,321 | |||||
| Issuance of common stock under dividend reinvestment plan | $ 1,500 | $ 1,100 | $ 1,300 | $ 1,100 | $ 1,000 | $ 900 | $ 800 | $ 800 | $ 600 | $ 500 | $ 500 | $ 500 | |||||
| Special | |||||||||||||||||
| Investment Company, Changes in Net Assets [Line Items] | |||||||||||||||||
| Amount per share (in dollars per share) | $ 0.42 | ||||||||||||||||
| Distributions to stockholders | $ 24,800 | ||||||||||||||||
| Issuance of common stock under dividend reinvestment plan (shares) | 41,510 | ||||||||||||||||
| Issuance of common stock under dividend reinvestment plan | $ 800 | ||||||||||||||||