Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income tax expense	$ 258.0	$ 291.8
Effective tax rate (percent)	23.20%	23.40%
Deferred tax assets net of DTL	$ 142.3		$ 182.4
Valuation allowance for deferred income taxes	$ 14.9		$ 14.9