Income Taxes - Schedule of Deferred Tax Assets (liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Deferred tax assets:
Compensation and benefit accruals not currently deductible	$ 81.8	$ 85.4
Net operating loss carryforwards	99.2	107.5
Self-insurance reserves	66.6	38.3
Research and experimentation and other tax credits	34.3	67.1
Pension liability	23.5	34.9
Accrued liabilities	263.3	265.7
Capital loss carryforward	13.0	49.5
Partnership investment	15.5	22.3
Other	12.2	8.2
Total deferred tax assets	609.4	678.9
Deferred tax liabilities:
Unearned revenue	(31.0)	(4.1)
Depreciation and amortization	(58.9)	(83.7)
Acquired intangible assets	(39.6)	0.0
Investment in subsidiaries	(9.8)	(9.9)
Right of use assets	(82.4)	(85.2)
Contingent consideration	0.0	(30.5)
Other	(3.3)	(5.4)
Total deferred tax liabilities	(225.0)	(218.8)
Valuation allowance	(157.1)	(160.9)
Net deferred tax assets	$ 227.3	$ 299.2