Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 559.1	$ 596.6	$ 1,129.8	$ 1,122.7
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	313.7	281.8	677.0	626.1
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	102.5	191.5	158.1	239.7
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	416.2	473.3	835.1	865.8
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	143.6	124.0	296.4	258.4
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (0.7)	$ (0.7)	$ (1.7)	$ (1.5)