Debt - Credit Agreement - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Jan. 31, 2023
Debt Instrument [Line Items]
Amount borrowed from credit facility foreign subsidiary	$ 241.3		$ 241.3
Interest expense	$ 19.6	$ 31.6	$ 41.7	$ 66.9
Interest rate during period	4.90%	5.50%	4.80%	5.60%
Line of Credit
Debt Instrument [Line Items]
Unused commitments under credit facility	$ 838.8		$ 838.8
Amounts available for borrowing	$ 823.3		$ 823.3
Line of Credit | Minimum
Debt Instrument [Line Items]
Credit facility commitment fees percentage			0.175%
Line of Credit | Maximum
Debt Instrument [Line Items]
Credit facility commitment fees percentage			0.325%
Secured Debt
Debt Instrument [Line Items]
Credit facility amount					$ 500.0
Annual rate for borrowings outstanding	5.90%		5.90%
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility amount					$ 1,250.0