Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 711.9	$ 651.9	$ 1,303.8	$ 1,206.3
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	345.2	309.7	747.4	672.0
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	208.2	226.0	244.2	281.8
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	553.4	535.7	991.6	953.8
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	159.7	117.1	314.4	254.4
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1.2)	$ (0.9)	$ (2.2)	$ (1.9)