Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 608.1	$ 657.2	$ 1,737.9	$ 1,779.9
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	454.9	486.4	1,132.0	1,112.6
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	5.1	5.7	163.1	245.4
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	460.0	492.1	1,295.1	1,358.0
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	149.1	166.3	445.5	424.7
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1.0)	$ (1.2)	$ (2.7)	$ (2.8)