Taxable/Distributable Income and Dividend Distributions - Schedule of Components of Accumulated Overdistributed Earnings (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Sep. 30, 2025
Income Tax Disclosure [Abstract]
Undistributed ordinary income, net		$ 2,986
Net realized capital losses		(646,358)
Unrealized losses, net		(241,771)
Accumulated overdistributed earnings	$ (967,901)	$ (885,143)

Amount of accumulated undistributed earnings (deficit).

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+ Details