Pension Plans - Schedule of Net Benefit Costs (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Interest cost	5.1	3.2	15.3	9.6
Expected return on plan assets	(5.2)	(5.7)	(15.7)	(17.1)
Amortization of unrecognized net losses	0.5	1.7	1.6	4.9
Net periodic cost/(benefit)	0.4	(0.8)	1.2	(2.6)
International
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.2	0.2	0.6
Interest cost	0.9	0.5	2.6	1.4
Expected return on plan assets	(0.8)	(0.9)	(2.2)	(2.6)
Amortization of unrecognized net losses	0.2	0.2	0.4	0.6
Net periodic cost/(benefit)	$ 0.3	$ 0.0	$ 1.0	$ 0.0