Income Taxes -Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Effective income tax rate	26.10%	21.20%	22.00%	20.20%
Unrecognized tax benefits, uncertain tax positions	$ 13.0		$ 13.0		$ 13.0
Unrecognized tax benefits, accrued interest	$ 0.8		$ 0.8		$ 0.5