Income Taxes - Unrecognized Tax Benefit (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 0.0	$ 1.4	$ 2.9
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	(1.4)	0.0
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	$ 0.0	$ (1.5)