Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 657,209	$ 630,330	$ 1,779,859	$ 1,771,800
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	486,451	465,668	1,112,596	1,088,785
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	5,654	8,913	245,356	252,590
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	492,105	474,581	1,357,952	1,341,375
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	166,319	157,379	424,692	433,620
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (1,215)	$ (1,630)	$ (2,785)	$ (3,195)