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Summary of Significant Accounting Policies - Revenue Recognition and Concentrations of Credit Risk - Additional Information (Detail)
$ in Thousands
12 Months Ended
Sep. 30, 2021
USD ($)
Customer
Sep. 30, 2020
USD ($)
Customer
Concentration Risk [Line Items]    
Number of customers with an account receivable balance of more than 10% of total accounts receivable | Customer 2 1
Allowance for doubtful accounts | $ $ 20,065 $ 23,419
Accounts Receivable [Member] | Customer [Member]    
Concentration Risk [Line Items]    
Aggregate account receivable of more than 10% of total accounts receivable 40.00% 22.00%