Recent Accounting Pronouncements - Additional Informaiton (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2018
New Accounting Pronouncement Early Adoption [Line Items]
Cumulative effect on retained earnings	$ 1,283.8	$ 1,342.7	$ 1,271.5	$ 1,227.3
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Accumulated Deficit
New Accounting Pronouncement Early Adoption [Line Items]
Cumulative effect on retained earnings	$ (146.3)	$ (141.6)	$ (187.9)	$ (189.6)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncement Early Adoption [Line Items]
Cumulative effect on retained earnings	(1.1)
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Deficit
New Accounting Pronouncement Early Adoption [Line Items]
Cumulative effect on retained earnings	$ (1.1)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member