Debt - Convertible Senior Notes Due 2024 (Details)			9 Months Ended
	Jul. 01, 2024 USD ($) shares	Jul. 05, 2017 USD ($) $ / shares	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
Amount outstanding			$ 367,762,000	$ 367,762,000	$ 367,762,000
Repayment of debt			0	178,488,000
Senior Notes
Debt Instrument [Line Items]
Amount outstanding			367,762,000
2024 Convertible Notes | Common Class A
Debt Instrument [Line Items]
Conversion rate per $1,000 principal amount		0.1
If-converted value in excess of principal amount			$ 800,000
Number of shares potentially issuable (in shares) | shares			77,000
2024 Convertible Notes | Common Class A | Subsequent Event
Debt Instrument [Line Items]
Debt conversion, further issued (in shares) | shares	77,328
2024 Convertible Notes | Senior Notes
Debt Instrument [Line Items]
Stated interest rate		2.875%
Principle amount		$ 143,750,000
Amount outstanding			$ 34,389,000	$ 34,389,000	$ 34,389,000
Effective interest rate			3.35%
Conversion price, per share (in dollars per share) | $ / shares		$ 10.00	$ 10.00
2024 Convertible Notes | Senior Notes | Subsequent Event
Debt Instrument [Line Items]
Repayment of debt	$ 34,400,000