Income Taxes - Summary of Income Tax Benefit and Effective Income Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
(Loss) before income taxes	$ (22.1)	$ (24.4)
Income tax (benefit)	$ (5.7)	$ (5.5)
Effective income tax rate	25.80%	22.50%