Taxes on Income - Reconciliation of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 342.9	$ 202.6	$ 77.5
Additions from business combinations	0.0	141.8	0.0
Additions for tax positions of prior years	4.2	0.9	131.8
Reductions for tax positions of prior years	(163.6)	(0.6)	(2.9)
Tax positions related to the current year	22.2	12.2	10.7
Settlements with taxing authorities	(3.2)	(0.3)	(2.2)
Expirations of statute of limitations	(18.2)	(13.7)	(12.3)
Balance at End of Year	$ 184.3	$ 342.9	$ 202.6