Discontinued Operations, Goodwill and Intangible Assets - Schedule of Balance Sheet Information of Assets and Liabilities Held for Sale (Details) - Held for Sale - USD ($) $ in Millions	Dec. 31, 2024	Sep. 30, 2024
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Cash and cash equivalents	$ 4.1	$ 4.0
Receivables and contract assets	63.0	73.2
Current assets held for sale	67.1	77.2
Property and equipment, net	17.1	16.7
Other	1.0	1.2
Write-down of assets to fair value less cost to sell	(18.1)	(17.9)
Non-current assets held for sale	0.0	0.0
Accounts payable and accrued expenses	25.3	35.6
Current liabilities held for sale	25.3	35.6
Long-term liabilities held for sale	$ 0.0	$ 0.0