Income Taxes -Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Effective income tax rate	7.30%	17.20%
Unrecognized tax benefits, uncertain tax positions	$ 14.8		$ 13.8
Unrecognized tax benefits, accrued interest	$ 1.2		$ 0.9