Share Data and Distributions - Schedule of Changes in Net Assets (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2024	Jun. 30, 2023
Investment Company, Net Assets [Roll Forward]
Beginning of period (in shares)			64,896,000				64,896,000
Net assets at beginning of period	$ 2,470,746	$ 2,005,171	$ 1,529,205	$ 724,860	$ 493,455	$ 366,727	$ 1,529,205	$ 366,727
Issuance of Common Shares in public offering	417,046	457,830	468,787	282,257	225,382	129,708
Issuance of Common Shares under dividend reinvestment plan	18,165	16,057	11,647	4,115	2,823	1,832	45,869	8,770
Shares repurchased, net of early repurchase deduction	(16,544)	(8,217)	(10,526)	(40)
Net investment income	61,642	53,929	35,803	18,908	11,804	10,097	151,374	40,809
Net unrealized appreciation (depreciation)	(3,198)	(655)	16,919	6,783	8,054	(2,842)
Net realized gains (losses)	(59)	3,347	453	(476)	(1,741)	(660)
Provision for income tax (expense) benefit	(158)	(144)	(241)	(71)	(54)	(51)	$ (543)	(176)
Distributions to shareholders	$ (68,254)	(56,572)	(46,876)	(21,422)	(14,863)	(11,356)
End of period (in shares)	122,364,000						122,364,000
Net assets at end of period	$ 2,879,386	$ 2,470,746	$ 2,005,171	$ 1,014,914	$ 724,860	$ 493,455	$ 2,879,386	$ 1,014,914
Common Shares
Investment Company, Net Assets [Roll Forward]
Beginning of period (in shares)	104,627	84,898	64,896	30,951	21,242	15,628	64,896	15,628
Net assets at beginning of period	$ 1,046	$ 849	$ 649	$ 310	$ 212	$ 156	$ 649	$ 156
Issuance of Common Shares in public offering (in shares)	17,673	19,399	19,952	12,093	9,589	5,536
Issuance of Common Shares in public offering	$ 177	$ 194	$ 199	$ 121	$ 97	$ 55
Issuance of Common Shares under dividend reinvestment plan (in shares)	767	679	496	177	120	78
Issuance of Common Shares under dividend reinvestment plan	$ 8	$ 7	$ 5	$ 1	$ 1	$ 1
Shares repurchased, net of early repurchase deduction (in shares)	(703)	(349)	(446)	(2)
Shares repurchased, net of early repurchase deduction	$ (7)	$ (4)	$ (4)	$ 0
End of period (in shares)	122,364	104,627	84,898	43,219	30,951	21,242	122,364	43,219
Net assets at end of period	$ 1,224	$ 1,046	$ 849	$ 432	$ 310	$ 212	$ 1,224	$ 432
Additional Paid-in-Capital
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period	2,471,486	2,006,013	1,536,305	740,237	512,130	380,646	1,536,305	380,646
Issuance of Common Shares in public offering	416,869	457,636	468,588	282,136	225,285	129,653
Issuance of Common Shares under dividend reinvestment plan	18,157	16,050	11,642	4,114	2,822	1,831
Shares repurchased, net of early repurchase deduction	(16,537)	(8,213)	(10,522)	(40)
Net assets at end of period	2,889,975	2,471,486	2,006,013	1,026,447	740,237	512,130	2,889,975	1,026,447
Accumulated Distributable Earnings (Loss)
Investment Company, Net Assets [Roll Forward]
Net assets at beginning of period	(1,786)	(1,691)	(7,749)	(15,687)	(18,887)	(14,075)	(7,749)	(14,075)
Net investment income	61,642	53,929	35,803	18,908	11,804	10,097
Net unrealized appreciation (depreciation)	(3,198)	(655)	16,919	6,783	8,054	(2,842)
Net realized gains (losses)	(59)	3,347	453	(476)	(1,741)	(660)
Provision for income tax (expense) benefit	(158)	(144)	(241)	(71)	(54)	(51)
Distributions to shareholders	(68,254)	(56,572)	(46,876)	(21,422)	(14,863)	(11,356)
Net assets at end of period	$ (11,813)	$ (1,786)	$ (1,691)	$ (11,965)	$ (15,687)	$ (18,887)	$ (11,813)	$ (11,965)