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Leases - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Lessee Lease Description [Line Items]    
Short term lease costs $ 5 $ 6
Variable lease cost $ 1 $ 1
Minimum [Member]    
Lessee Lease Description [Line Items]    
Lease term 1 year  
Maximum [Member]    
Lessee Lease Description [Line Items]    
Lease term 18 years  
Lease extension period 15 years  
Maximum [Member] | Land [Member]    
Lessee Lease Description [Line Items]    
Lease term 69 years