Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2021	Sep. 30, 2020
Property Plant And Equipment [Line Items]
Property and equipment	$ 656.4	$ 614.4
Less: Accumulated depreciation	394.6	362.9
Property and equipment, net	261.8	251.5
Land
Property Plant And Equipment [Line Items]
Property and equipment	42.2	40.0
Building and Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment	31.3	30.3
Operating Equipment
Property Plant And Equipment [Line Items]
Property and equipment	231.3	208.2
Transportation Vehicles
Property Plant And Equipment [Line Items]
Property and equipment	276.3	262.8
Office Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment	70.5	68.1
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment	$ 4.8	$ 5.0
Minimum \| Building and Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	2 years
Minimum \| Operating Equipment
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	2 years
Minimum \| Transportation Vehicles
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	3 years
Minimum \| Office Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	3 years
Maximum \| Building and Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	40 years
Maximum \| Operating Equipment
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	7 years
Maximum \| Transportation Vehicles
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	7 years
Maximum \| Office Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, Useful Life	10 years

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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