Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 554.4	$ 570.7
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	362.2	363.3
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	55.8	55.6
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	418.0	418.9
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	137.4	152.8
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1.0)	$ (1.0)