Fair Value Measurements - Balance Sheet Classification (Details ) - USD ($) $ in Millions | Oct. 31, 2017 | Jul. 31, 2017 |
Cash and cash equivalents | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total cash equivalents | $ 529 | $ 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 | 28 | 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 | 28 | 181 |
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 | 28 | 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 | 28 | 181 |
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 | 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 | 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 |