Supplemental Financial Information - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	$ 526.7	$ 23.4	$ 25.5
Total cash, cash equivalents and restricted cash	526.7	83.9	99.6	$ 231.4
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	0.0	59.0	72.6
Restricted cash - discontinued operations (a)	$ 0.0	$ 1.5	$ 1.5