Borrowings - Narrative (Details) - USD ($)			1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 01, 2022	Jun. 01, 2012	Oct. 31, 2023	Jan. 31, 2010	Sep. 30, 2023	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Oct. 12, 2023	Oct. 31, 2022	Oct. 13, 2022
Debt Instrument [Line Items]
(Loss) gain on extinguishment of debt, net							$ (546,000)	$ 309,000	$ (2,025,000)
Senior Notes
Debt Instrument [Line Items]
(Loss) gain on extinguishment of debt, net								(300,000)
Senior Notes | 6.750% Senior Notes (2025 Notes)
Debt Instrument [Line Items]
Extinguishment of debt							9,000,000	18,400,000
(Loss) gain on extinguishment of debt, net							100,000
Senior Notes | 6.750% Senior Notes (2025 Notes) | Subsequent Event
Debt Instrument [Line Items]
Extinguishment of debt			$ 4,300,000
(Loss) gain on extinguishment of debt, net			100,000
Senior Notes | 6.750% Senior Notes (2025 Notes) | Maximum | Subsequent Event
Debt Instrument [Line Items]
Outstanding balance of notes			$ 197,900,000
Senior Notes | 5.875% Senior Notes (2027 Notes)
Debt Instrument [Line Items]
Extinguishment of debt								6,000,000	30,700,000
(Loss) gain on extinguishment of debt, net									$ 2,000,000
Junior Subordinated Notes
Debt Instrument [Line Items]
Aggregate principle balance of notes					$ 100,800,000		$ 100,800,000
Weighted average fixed interest rate of debt (percent)					8.08%		8.08%
Unamortized discount					$ 26,400,000		$ 26,400,000
Junior Subordinated Debt, Modified Terms
Debt Instrument [Line Items]
Aggregate principal amount of debt				$ 75,000,000
Redemption price percentage		75.00%
Annual increase of percentage of principal amount redeemable	1.785%
Junior Subordinated Debt, Modified Terms | LIBOR
Debt Instrument [Line Items]
Variable rate floor				4.25%
Variable rate cap				9.25%
Junior Subordinated Debt, Original Terms
Debt Instrument [Line Items]
Aggregate principal amount of debt					$ 25,800,000		25,800,000
Junior Subordinated Debt, Original Terms | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate					2.71%	2.45%
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity											$ 250,000,000	$ 265,000,000
Credit facility, available increase in borrowing capacity												135,000,000
Secured Revolving Credit Facility					$ 0		0	0
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
(Loss) gain on extinguishment of debt, net							500,000
Revolving Credit Facility | Subsequent Event
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity										$ 300,000,000
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity												$ 400,000,000
Letter of Credit
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity					100,000,000		100,000,000
Letters of credit secured using cash collateral					$ 31,200,000		$ 31,200,000	$ 29,700,000