Debt - Senior Notes (Details) - USD ($)		12 Months Ended
	Apr. 16, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Apr. 29, 2024
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt		$ (5,100,000)	$ 0	$ 0
Line of Credit | Revolver
Debt Instrument [Line Items]
Proceeds from long-term lines of credit	$ 175,000,000.0
2031 Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate of debt		3.625%
Aggregate principal amount		$ 535,000,000.0	535,000,000.0
2030 Notes
Debt Instrument [Line Items]
Debt instrument, repurchase amount	$ 598,300,000				$ 1,700,000
Gain (loss) on extinguishment of debt		(5,100,000)
2030 Notes | Senior Notes
Debt Instrument [Line Items]
Interest rate of debt	4.25%
Aggregate principal amount	$ 600,000,000.0	$ 0	$ 600,000,000.0
Percent of principal amount redeemed	99.70%