Fair Value of Financial Instruments - Reconciliation of Liabilities Measured at Fair Value Using Significant Unobservable Inputs Level 3 (Details) - Level 3 - Long-Term Credit Facility - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 376,687	$ 314,813
Net change in unrealized appreciation (depreciation) included in earnings	(4,379)	996
Borrowings	44,000	416,897
Repayments	(49,000)	(288,218)
Ending Balance	$ 367,308	$ 444,488