Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 2,553.6	$ 2,346.0	$ 2,404.6
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	1,698.0	1,566.3	1,568.3
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	284.9	163.1	245.1
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	1,982.9	1,729.4	1,813.4
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	574.9	620.3	595.4
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (4.2)	$ (3.7)	$ (4.2)