Property and Equipment Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Net Book Value of Capitalized Internal-Use Software	$ 6.9	$ 2.2
Depreciation expense	9.2	6.2	$ 7.7
Amortization expense	$ 3.1	$ 2.7	$ 4.2