Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income tax expense	$ 15.4	$ 9.2	$ 28.4	$ 16.3
Effective income tax rate, percent	24.40%	24.50%	24.30%	24.40%
Deferred Income Tax Liabilities, Net of Deferred Income Tax Assets	$ 21.9		$ 21.9		$ 23.2
Valuation allowance, deferred tax asset, amount	1.1		1.1		1.2
Deferred tax liability, net	$ 23.0		$ 23.0		$ 24.4