Borrowings - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	$ 1,071,290	$ 1,025,349
Unamortized debt issuance costs	(7,885)	(8,310)
Senior Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Senior Unsecured Revolving Credit Facility	45,000	0
Senior Notes
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	949,370	948,945
Unamortized debt issuance costs	$ (7,885)	$ (8,310)
Senior Notes | 5.875%
Debt Instrument [Line Items]
Stated interest rate on debt instrument	5.875%	5.875%
Total outstanding borrowings of unconsolidated entities	$ 357,255	$ 357,255
Senior Notes | 7.250%
Debt Instrument [Line Items]
Stated interest rate on debt instrument	7.25%	7.25%
Total outstanding borrowings of unconsolidated entities	$ 350,000	$ 350,000
Senior Notes | 7.500%
Debt Instrument [Line Items]
Stated interest rate on debt instrument	7.50%
Total outstanding borrowings of unconsolidated entities	$ 250,000	250,000
Junior Subordinated Notes
Debt Instrument [Line Items]
Unamortized accretion	23,853	24,369
Total outstanding borrowings of unconsolidated entities	$ 76,920	$ 76,404