v3.23.3
Financial Highlights - Portfolio Composition (Details)
$ / shares in Units, shares in Thousands, $ in Thousands
 12 Months Ended
Jun. 30, 2023
$ / shares
Mar. 31, 2023
$ / shares
Jan. 20, 2023
Jun. 30, 2022
$ / shares
Mar. 31, 2022
$ / shares
Dec. 31, 2021
$ / shares
Sep. 30, 2023
USD ($)
$ / shares
shares
Sep. 30, 2022
USD ($)
$ / shares
shares
Sep. 30, 2021
USD ($)
$ / shares
shares
Sep. 30, 2020
USD ($)
$ / shares
shares
Sep. 30, 2019
USD ($)
$ / shares
shares
Investment Company, Financial Highlights [Roll Forward]                      
Net asset value per share at beginning of period (in dollars per share)             $ 20.38 [1] $ 21.84 [1] $ 19.47 $ 19.81 $ 18.26
Net investment income (in dollars per share)             2.51 [2] 2.45 [2] 1.80 [2] 1.53 1.45
Net unrealized appreciation (depreciation) (in dollars per share)             (0.17) (2.23) 2.19 (0.44) 0.82
Net realized gains (losses) (in dollars per share)             (0.46) 0.28 0.49 (0.30) 0.44
(Provision) benefit for taxes on realized and unrealized gains (losses) (in dollars per share)             (0.02) (0.01) (0.02) 0.04 (0.02)
Distributions of net investment income to stockholders (dollars per share)             (2.61) (1.95) (1.515) (1.17) (1.14)
Issuance of common stock (in dollars per share)             0 0 (0.57) 0 0
Net asset value per share at end of period (in dollars per share) $ 19.58 $ 19.66   $ 20.67 $ 21.79 $ 22.03 19.63 [1] 20.38 [1] 21.84 [1] 19.47 19.81
Per share market value at beginning of period (in dollars per share)             18.00 21.18 14.52 15.54 14.88
Per share market value at end of period (in dollars per share)             $ 20.12 $ 18.00 $ 21.18 $ 14.52 $ 15.54
Total return             27.30% (6.71%) 57.61% 2.10% 12.56%
Common shares outstanding at beginning of period (in shares) | shares             61,125 [1] 60,120 [1] 46,987 46,987 46,987
Common shares outstanding at end of period (in shares) | shares             77,225 [1] 61,125 [1] 60,120 [1] 46,987 46,987
Net assets at beginning of period | $             $ 1,245,563 $ 1,312,823 $ 914,879 $ 930,630 $ 858,035
Net assets at end of period | $             1,515,764 1,245,563 1,312,823 914,879 930,630
Average net assets | $             $ 1,437,728 $ 1,308,518 $ 1,150,662 $ 871,305 $ 909,264
Ratio of net investment income to average net assets             12.57% 11.36% 8.44% 8.26% 7.47%
Ratio of total expenses to average net assets             14.19% 8.68% 9.65% 7.57% 9.65%
Ratio of net expenses to average net assets             13.81% 8.45% 9.51% 8.16% 8.78%
Ratio of portfolio turnover to average investments at fair value             26.12% 26.99% 39.66% 38.99% 32.50%
Weighted average outstanding debt | $             $ 1,659,701 $ 1,361,151 $ 964,390 $ 647,080 $ 573,891
Average debt per share (dollars per share)             $ 23.01 $ 22.41 $ 17.85 $ 13.77 $ 12.21
Asset coverage ratio             187.74% 188.64% 201.68% 227.22% 294.91%
Stock split, conversion ratio     0.0033       0.3333        
[1] As discussed in Note 2, the Company completed a 1-for-3 reverse stock split on January 20, 2023, effective as of the commencement of trading on January 23, 2023. The weighted average common shares outstanding and per share information reflect the reverse stock split on a retroactive basis.
[2] As discussed in Note 2, the Company completed a 1-for-3 reverse stock split on January 20, 2023, effective as of the commencement of trading on January 23, 2023. The weighted average common shares outstanding and per share information reflect the reverse stock split on a retroactive basis.