Intangible Assets, Goodwill, Acquisitions and Divestitures - Additional Information (Details) $ in Millions			12 Months Ended
		Jan. 12, 2024 USD ($) Subsidiary	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($) Company	Sep. 30, 2022 USD ($)
Finite Lived Intangible Assets [Line Items]
Amortization of intangible assets			$ 35.8	$ 44.5	$ 51.5
Intangible assets acquired			0.0
Weighted average amortization period for intangible assets				7 years
Number of unrelated maintenance services companies acquired | Company				3
Consideration paid, net of cash acquired			0.0	$ 13.8	93.1
Net service revenues			2,767.1	2,816.0	2,774.6
Number of sale of fully owned subsidiaries | Subsidiary		1
Cash consideration		$ 51.0	$ 51.0	$ 0.0	$ 0.0
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal, Statement of Income or Comprehensive Income [Extensible Enumeration]			Gain (Loss) on Disposition of Business	Gain (Loss) on Disposition of Business	Gain (Loss) on Disposition of Business
Pre-tax gain (loss) on sale of business	[1]		$ (43.6)	$ 0.0	$ 0.1
Unrelated Maintenance Services Companies
Finite Lived Intangible Assets [Line Items]
Acquisition of operations, Percentage				100.00%
Consideration paid, net of cash acquired				$ 13.8
Business Acquisitions
Finite Lived Intangible Assets [Line Items]
Net service revenues				16.0
Selling, General and Administrative Expense
Finite Lived Intangible Assets [Line Items]
Gain on Sale of Fully Owned Subsidiaries			$ 43.6
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Identifiable assets acquired related to intangible assets				$ 4.0

[1] Represents the realized gain on sale and transaction related expenses from the divestiture of U.S. Lawns on January 12, 2024.