Fair Value Measurements - Balance Sheet Classification (Details) - USD ($) $ in Millions	Oct. 31, 2020	Jul. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	$ 5,174	$ 6,442
Available-for-sale debt securities:	819	808
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Held-for-sale, Fair Value Disclosure		98
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	4,016	5,765
Available-for-sale debt securities:	819	808
Fair value, measurements, recurring | In cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	4,016	5,765
Fair value, measurements, recurring | Available for sale debt securities in investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	619	608
Fair value, measurements, recurring | Available for sale debt securities in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	200	200
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	4,016	5,765
Available-for-sale debt securities:	0	0
Fair value, measurements, recurring | Level 1 | In cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	4,016	5,765
Fair value, measurements, recurring | Level 1 | Available for sale debt securities in investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0	0
Fair value, measurements, recurring | Level 1 | Available for sale debt securities in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	0	0
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Available-for-sale debt securities:	819	808
Fair value, measurements, recurring | Level 2 | In cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Fair value, measurements, recurring | Level 2 | Available for sale debt securities in investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	619	608
Fair value, measurements, recurring | Level 2 | Available for sale debt securities in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities:	$ 200	$ 200