Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Effective income tax rate	5.70%	33.50%
U.S. statutory rate	21.00%	21.00%
Gross unrecognized tax benefits	$ 19.9		$ 20.1
Accrued interest and penalties related to unrecognized tax benefits	3.5		$ 3.3
Reasonably possible amount of reduction in gross unrecognized tax benefits for the next twelve months	18.5
Reasonably possible amount of net reduction to income tax provision if unrecognized tax benefits were recognized	$ 19.9