Fair Value Measurements (Details) - USD ($) $ in Millions | Apr. 30, 2016 | Jul. 31, 2015 |
Liabilities: | | | |
Long-term debt | | $ 500 | $ 500 |
Short-term debt | | 500 | 0 |
Fair value, measurements, recurring | Estimate of fair value measurement | | | |
Assets: | | | |
Total cash equivalents | | 729 | 695 |
Available-for-sale debt securities: | | | |
Total assets measured at fair value on a recurring basis | | 1,243 | 1,774 |
Liabilities: | | | |
Senior notes | [1] | 520 | 531 |
Fair value, measurements, recurring | Estimate of fair value measurement | Municipal bonds | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 175 | 506 |
Fair value, measurements, recurring | Estimate of fair value measurement | Corporate notes | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 241 | 546 |
Fair value, measurements, recurring | Estimate of fair value measurement | U.S. agency securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 83 | 12 |
Fair value, measurements, recurring | Estimate of fair value measurement | Municipal auction rate securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 15 | 15 |
Fair value, measurements, recurring | Estimate of fair value measurement | Available-for-sale corporate equity securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 514 | 1,079 |
Fair value, measurements, recurring | Level 1 | | | |
Assets: | | | |
Total cash equivalents | | 729 | 695 |
Available-for-sale debt securities: | | | |
Total assets measured at fair value on a recurring basis | | 729 | 695 |
Liabilities: | | | |
Senior notes | [1] | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Municipal bonds | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Corporate notes | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 1 | U.S. agency securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Municipal auction rate securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Available-for-sale corporate equity securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 2 | | | |
Assets: | | | |
Total cash equivalents | | 0 | 0 |
Available-for-sale debt securities: | | | |
Total assets measured at fair value on a recurring basis | | 499 | 1,064 |
Liabilities: | | | |
Senior notes | [1] | 520 | 531 |
Fair value, measurements, recurring | Level 2 | Municipal bonds | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 175 | 506 |
Fair value, measurements, recurring | Level 2 | Corporate notes | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 241 | 546 |
Fair value, measurements, recurring | Level 2 | U.S. agency securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 83 | 12 |
Fair value, measurements, recurring | Level 2 | Municipal auction rate securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 2 | Available-for-sale corporate equity securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 499 | 1,064 |
Fair value, measurements, recurring | Level 3 | | | |
Assets: | | | |
Total cash equivalents | | 0 | 0 |
Available-for-sale debt securities: | | | |
Total assets measured at fair value on a recurring basis | | 15 | 15 |
Liabilities: | | | |
Senior notes | [1] | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Municipal bonds | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Corporate notes | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 3 | U.S. agency securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Municipal auction rate securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 15 | 15 |
Fair value, measurements, recurring | Level 3 | Available-for-sale corporate equity securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | $ 15 | $ 15 |
| |
[1] | Carrying value on our balance sheets at April 30, 2016 was $500 million and at July 31, 2015 was $500 million. See Note 5, “Current Liabilities – Short-Term Debt,” for more information. | |