Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 591.8	$ 554.4
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	402.2	362.2
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	36.0	55.8
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	438.2	418.0
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	154.7	137.4
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1.1)	$ (1.0)