Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 747.4	$ 673.6	$ 2,051.2	$ 1,879.9
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	548.9	521.2	1,296.3	1,193.2
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	12.9	3.4	257.1	285.2
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	561.8	524.6	1,553.4	1,478.4
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	186.4	150.3	500.8	404.7
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (0.8)	$ (1.3)	$ (3.0)	$ (3.2)