Income Taxes - Additional Information - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income tax expense	$ 3.3	$ 3.6	$ 8.7	$ 4.6
Effective income tax rate, percent	24.10%	22.00%	24.30%	21.60%
Deferred Tax Assets, Net Of Deferred Tax Liabilities	$ 11.3		$ 11.3		$ 20.7
Valuation allowance, deferred tax asset, amount	3.3		3.3		$ 3.3
Unrecognized tax benefits	$ 1.6		$ 1.6