Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 738.8	$ 766.0	$ 2,038.4	$ 2,072.3
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	516.2	555.3	1,256.3	1,335.8
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	8.5	9.3	221.2	209.9
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	524.7	564.6	1,477.5	1,545.7
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	215.0	203.4	564.8	533.3
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (0.9)	$ (2.0)	$ (3.9)	$ (6.7)