Borrowings - Schedule of Long-term Debt (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Oct. 31, 2022	Oct. 13, 2022	Sep. 30, 2022	Sep. 30, 2019	Oct. 31, 2017	Mar. 31, 2017
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	$ 981,128,000		$ 981,128,000				$ 983,440,000
Unamortized debt issuance costs	(6,142,000)		(6,142,000)				(7,280,000)
Loss on extinguishment of debt, net	18,000	$ (86,000)	$ 533,000	$ 78,000
Senior Notes
Debt Instrument [Line Items]
Loss on extinguishment of debt, net	$ 100,000			$ 100,000
6.750% | Senior Notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument	6.75%		6.75%							6.75%
Loss on extinguishment of debt, net		$ 100,000
5.875% | Senior Notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument	5.875%		5.875%						5.875%
7.250% | Senior Notes
Debt Instrument [Line Items]
Stated interest rate on debt instrument	7.25%		7.25%					7.25%
Secured Revolving Credit Facility
Debt Instrument [Line Items]
Secured Revolving Credit Facility	$ 0		$ 0				0
Credit facility, maximum borrowing capacity					$ 250,000,000	$ 265,000,000
Loss on extinguishment of debt, net			500,000
Letters of credit secured using cash collateral	0		0				5,500,000
Line of credit facility, remaining borrowing capacity	265,000,000		265,000,000				244,500,000
Senior Notes
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	907,308,000		907,308,000				911,170,000
Unamortized debt issuance costs	(6,142,000)		(6,142,000)				(7,280,000)
Senior Notes | 6.750%
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	206,195,000		206,195,000				211,195,000
Senior Notes | 5.875%
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	357,255,000		357,255,000				357,255,000
Senior Notes | 7.250%
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	350,000,000		350,000,000				350,000,000
Junior Subordinated Notes
Debt Instrument [Line Items]
Total outstanding borrowings of unconsolidated entities	$ 73,820,000		$ 73,820,000				$ 72,270,000