Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income tax expense	$ 432.2	$ 524.0	$ 1,026.7	$ 1,316.5
Effective tax rate (percent)	24.20%	24.00%	23.90%	23.70%
Deferred tax assets net of DTL	$ 139.6		$ 139.6		$ 159.0
Valuation allowance for deferred income taxes	$ 17.8		$ 17.8		$ 17.9