Significant Accounting Policies - Schedule of Sales Disaggregated by Segment and Geographical Area (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Net revenues	$ 1,443.5	$ 1,236.1	$ 1,037.2
United States
Disaggregation of Revenue [Line Items]
Net revenues	1,407.7	1,191.8	997.3
Non-U.S.
Disaggregation of Revenue [Line Items]
Net revenues	$ 35.8	$ 44.3	$ 39.9