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Supplementary Financial Information - Allowance for Doubtful Accounts (Details)
$ in Millions
6 Months Ended
Apr. 30, 2021
USD ($)
Accounts Receivable, Allowance for Credit Loss [Roll Forward]  
Balance at beginning of period $ 122
Current-period allowance for credit losses 23
Deductions, net of recoveries (12)
Balance at end of period $ 133