Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income tax expense	$ 351.5	$ 239.1
Effective tax rate (percent)	23.50%	23.10%
Deferred tax assets net of DTL	$ 141.7		$ 159.5
Valuation allowance for deferred income taxes	$ 4.1		$ 4.2