Borrowings - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Sep. 30, 2025
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	$ 1,409,132	$ 1,029,114
Unamortized debt issuance costs	(10,888)	(6,611)
Senior Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Senior Unsecured Revolving Credit Facility	340,000	0
Senior Notes
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	989,112	950,644
Unamortized debt issuance costs	$ (10,888)	$ (6,611)
Senior Notes \| 5.875%
Debt Instrument [Line Items]
Stated interest rate on debt instrument	5.875%	5.875%
Total outstanding borrowings of unconsolidated entities	$ 0	$ 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%	7.50%
Total outstanding borrowings of unconsolidated entities	$ 250,000	$ 250,000
Senior Notes \| 8.000%
Debt Instrument [Line Items]
Stated interest rate on debt instrument	8.00%	8.00%
Total outstanding borrowings of unconsolidated entities	$ 400,000	$ 0
Junior Subordinated Notes
Debt Instrument [Line Items]
Unamortized accretion	20,753	22,303
Total outstanding borrowings of unconsolidated entities	$ 80,020	$ 78,470