Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 708.3	$ 738.8	$ 1,970.0	$ 2,038.4
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	502.9	516.2	1,200.2	1,256.3
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	5.9	8.5	210.7	221.2
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	508.8	524.7	1,410.9	1,477.5
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	201.3	215.0	565.0	564.8
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1.8)	$ (0.9)	$ (5.9)	$ (3.9)