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Contingencies, Significant Estimates and Concentrations - Additional Information (Details) - USD ($)
9 Months Ended
Jun. 30, 2021
Sep. 30, 2020
Personal Injury Actions and Other    
Loss Contingencies [Line Items]    
Maximum self-insurance available per claim $ 5,000,000.0  
Reserve for loss contingencies 38,600,000 $ 33,800,000
Performance and Specialty Bonds    
Loss Contingencies [Line Items]    
Commitments and contingencies 1,000,000,000.0 721,100,000
Standby Letters of Credit    
Loss Contingencies [Line Items]    
Commitments and contingencies $ 22,800,000 $ 64,400,000