Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 2,816.0	$ 2,774.6	$ 2,553.6
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	1,857.5	1,825.7	1,698.0
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	209.0	256.3	284.9
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	2,066.5	2,082.0	1,982.9
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	758.0	698.8	574.9
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (8.5)	$ (6.2)	$ (4.2)