Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 2,774.6	$ 2,553.6	$ 2,346.0
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	1,825.7	1,698.0	1,566.3
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	256.3	284.9	163.1
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	2,082.0	1,982.9	1,729.4
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	698.8	574.9	620.3
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (6.2)	$ (4.2)	$ (3.7)