Annual report pursuant to Section 13 and 15(d)

Other Balance Sheet Components - Accounts Receivable, Net (Details)

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Other Balance Sheet Components - Accounts Receivable, Net (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Allowance for credit losses $ (8,273) $ (8,044)  
Accounts receivable, net 807,110 834,819  
Accounts Receivable, Allowance for Credit Loss [Roll Forward]      
Balance at beginning of period 8,044 6,051 $ 5,382
Provision for estimated credit losses 6,799 11,038 12,976
Write-offs, net of recoveries (6,570) (9,045) (12,307)
Balance at end of period 8,273 8,044 $ 6,051
Billed and billable receivables      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accounts Receivable Gross 723,979 718,728  
Unbilled receivables      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Accounts Receivable Gross $ 91,404 $ 124,135