Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 570.7	$ 526.0
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	363.3	344.5
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	55.6	48.0
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	418.9	392.5
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	152.8	134.4
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1.0)	$ (0.9)