Other Balance Sheet Information - Capitalized Direct Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Sep. 30, 2022
Property, Plant and Equipment, Gross [Abstract]
Capitalized computer software, gross	$ 28.7		$ 28.7		$ 26.9
Capitalized computer software costs	0.7	$ 0.8	1.8	$ 1.3
Software Development
Property, Plant and Equipment, Gross [Abstract]
Capitalized computer software, gross	$ 10.2		$ 10.2