Income Taxes - Unrecognized Tax Benefit (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 1.4	$ 2.9	$ 2.9
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	0.0	0.0
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(1.5)	0.0
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 1.4	$ 2.9