Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Effective income tax rate	15.80%	5.70%
U.S. statutory rate	21.00%	21.00%
Income tax liabilities	$ 296.0		$ 296.0
Gross unrecognized tax benefits	22.5		25.5
Accrued interest and penalties related to unrecognized tax benefits	4.2		$ 4.0
Reasonably possible amount of reduction in gross unrecognized tax benefits for the next twelve months	22.1
Reasonably possible amount of net reduction to income tax provision if unrecognized tax benefits were recognized	$ 25.6