Income Taxes -Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Effective income tax rate	18.90%	1.70%
Unrecognized tax benefits, uncertain tax positions	$ 11.8		$ 10.9
Unrecognized tax benefits, accrued interest	$ 0.5		$ 0.4