Fair Value Measurements - Balance Sheet Classification (Details ) - USD ($) $ in Millions	Jan. 31, 2018	Jul. 31, 2017
Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	$ 478	$ 529
Fair value, measurements, recurring | Estimate of fair value measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	202	181
Total available-for-sale securities	463	463
Fair value, measurements, recurring | Estimate of fair value measurement | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	172	181
Fair value, measurements, recurring | Estimate of fair value measurement | Cash equivalents in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	30	0
Fair value, measurements, recurring | Estimate of fair value measurement | Available for sale debt securities in investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	248	248
Fair value, measurements, recurring | Estimate of fair value measurement | Available for sale debt securities in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	200	200
Fair value, measurements, recurring | Estimate of fair value measurement | Available for sale debt securities in long term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	15	15
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	202	181
Total available-for-sale securities	0	0
Fair value, measurements, recurring | Level 1 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	172	181
Fair value, measurements, recurring | Level 1 | Cash equivalents in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	30	0
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]
Total available-for-sale 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]
Total available-for-sale securities	0	0
Fair value, measurements, recurring | Level 1 | Available for sale debt securities in long term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	0	0
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Total available-for-sale securities	448	448
Fair value, measurements, recurring | Level 2 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value, measurements, recurring | Level 2 | Cash equivalents in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total 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]
Total available-for-sale securities	248	248
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]
Total available-for-sale securities	200	200
Fair value, measurements, recurring | Level 2 | Available for sale debt securities in long term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	0	0
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Total available-for-sale securities	15	15
Fair value, measurements, recurring | Level 3 | Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value, measurements, recurring | Level 3 | Cash equivalents in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total cash equivalents	0	0
Fair value, measurements, recurring | Level 3 | Available for sale debt securities in investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	0	0
Fair value, measurements, recurring | Level 3 | Available for sale debt securities in funds held for customers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	0	0
Fair value, measurements, recurring | Level 3 | Available for sale debt securities in long term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities	$ 15	$ 15