Taxable/Distributable Income - Schedule of Reconciliation of Net Increase (Decrease) in Net Assets Resulting from Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Income Tax Disclosure [Abstract]
Net increase (decrease) in net assets resulting from operations	$ 83,427	$ 83,755	$ 150,380	$ 213,435
Net unrealized (appreciation) depreciation	(2,075)	(16,793)	108,081	13,157
Book/tax difference due to capital gains incentive fees	(1,211)	100	(1,211)	(2,372)
Other book/tax differences	13,928	(13,743)	40,480	(11,508)
Taxable income	$ 94,069	$ 53,319	$ 297,730	$ 212,712