Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 717.6	$ 708.3	$ 2,035.3	$ 1,970.0
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	514.5	502.9	1,215.5	1,200.2
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	3.4	5.9	293.4	210.7
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	517.9	508.8	1,508.9	1,410.9
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	201.9	201.3	530.7	565.0
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (2.2)	$ (1.8)	$ (4.3)	$ (5.9)