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Income Taxes - Additional information (Details) - USD ($) $ in Millions		12 Months Ended			36 Months Ended
	Apr. 01, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2023
Income taxes
Effective tax rate (as a percent)		26.30%	24.70%	21.80%
Valuation allowance related to net deferred tax assets		$ 171.2	$ 154.4		$ 171.2
Corporate tax rate		21.00%	21.00%	21.00%	21.00%
Tax expense related to audit settlement				$ 13.2
Tax rate changes		$ (3.2)	$ (4.1)	(26.8)
Tax benefit from foreign subsidiaries		$ (52.8)	(75.8)	$ (53.2)
United Kingdom
Income taxes
Corporate tax rate	25.00%			19.00%
Tax rate changes				$ 25.9
Foreign [Member]
Income taxes
Valuation allowance related to net operating losses			$ 21.9