Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 207.1	$ 116.3	$ 169.6
Other comprehensive (loss)/income, net of tax:
Foreign currency translation adjustment	(11.7)	13.3	(4.5)
Cash flow hedges	(53.5)	0.0	0.0
Pension liabilities adjustment	(0.3)	1.5	(0.2)
Reclassification of adjustment for losses included in net income:
Periodic pension costs (included in compensation and benefits)	0.0	0.2	0.1
Reclassification adjustment for losses included in net income	0.0	0.2	0.1
Other comprehensive (loss)/income	(65.5)	15.0	(4.6)
Comprehensive income	$ 141.6	$ 131.3	$ 165.0