Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 596,637	$ 590,382	$ 1,122,650	$ 1,141,471
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	281,777	270,014	626,145	623,118
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	191,537	190,091	239,702	243,677
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	473,314	460,105	865,847	866,795
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	123,977	131,018	258,373	276,241
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (654)	$ (741)	$ (1,570)	$ (1,565)