Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 2,672.8	$ 2,767.1	$ 2,816.0
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	1,680.5	1,743.2	1,857.5
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	210.8	220.8	209.0
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	1,891.3	1,964.0	2,066.5
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	789.1	808.8	758.0
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (7.6)	$ (5.7)	$ (8.5)