Debt - Convertible Senior Notes Due 2024 (Details) - USD ($)		12 Months Ended
	Jul. 01, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Jul. 05, 2017
Debt Instrument [Line Items]
Long-term debt		$ 327,328,000	$ 360,112,000
Payments on assumed debt		34,389,000	178,488,000	$ 0
2024 Convertible Notes | Common Class A
Debt Instrument [Line Items]
Debt conversion, further issued (in shares)	77,328
2024 Convertible Notes | Senior Notes
Debt Instrument [Line Items]
Stated interest rate					2.875%
Debt instrument, face amount					$ 143,750,000
Long-term debt		$ 0	$ 34,265,000
Payments on assumed debt	$ 34,400,000