Revenue - Schedule of Reportable Segment Revenues, Disaggregated by Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Disaggregation Of Revenue [Line Items]
Net service revenues	$ 2,767.1	$ 2,816.0	$ 2,774.6
Operating Segments | Landscape Maintenance
Disaggregation Of Revenue [Line Items]
Net service revenues	1,743.2	1,857.5	1,825.7
Operating Segments | Snow Removal
Disaggregation Of Revenue [Line Items]
Net service revenues	220.8	209.0	256.3
Operating Segments | Maintenance Services
Disaggregation Of Revenue [Line Items]
Net service revenues	1,964.0	2,066.5	2,082.0
Operating Segments | Development Services
Disaggregation Of Revenue [Line Items]
Net service revenues	808.8	758.0	698.8
Eliminations
Disaggregation Of Revenue [Line Items]
Net service revenues	$ (5.7)	$ (8.5)	$ (6.2)