Income Taxes -Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Effective income tax rate	18.40%	22.70%	20.60%	21.00%
Unrecognized tax benefits, uncertain tax positions	$ 14.3		$ 14.3		$ 13.0
Unrecognized tax benefits, accrued interest	$ 1.0		$ 1.0		$ 0.5