Income Taxes - Schedule of Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022	Sep. 30, 2021	Sep. 30, 2020
Reconciliation of the beginning and ending amount of unrecognized tax benefits
Balance at beginning of period	$ 46.0	$ 41.5	$ 79.8	$ 97.3
Additions for tax positions related to current year	0.5	50.2	15.8	46.2
Additions for tax positions related to prior years		20.9	0.6	1.4
Reductions for tax positions related to prior years	(5.0)	(10.0)	(46.0)	(61.8)
Settlements				(1.3)
Foreign currency translation		(1.9)
Lapse of statutes of limitations		(1.9)	(4.2)	(2.0)
Balance at end of period	$ 41.5	$ 98.8	$ 46.0	$ 79.8