Fair Value Measurements (Details) - USD ($) $ in Millions | Oct. 31, 2015 | Jul. 31, 2015 |
Liabilities: | | | |
Long-term debt | | $ 500 | $ 500 |
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | | | |
Assets: | | | |
Total cash equivalents | | 262 | 695 |
Available-for-sale debt securities: | | | |
Total assets measured at fair value on a recurring basis | | 452 | 1,774 |
Liabilities: | | | |
Senior notes | [1] | 530 | 531 |
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Municipal bonds | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 6 | 506 |
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | Corporate notes | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 169 | 546 |
Fair Value, Measurements, Recurring | Estimate of Fair Value Measurement | U.S. agency securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 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 | | 190 | 1,079 |
Fair Value, Measurements, Recurring | Level 1 | | | |
Assets: | | | |
Total cash equivalents | | 262 | 695 |
Available-for-sale debt securities: | | | |
Total assets measured at fair value on a recurring basis | | 262 | 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 | | 175 | 1,064 |
Liabilities: | | | |
Senior notes | [1] | 530 | 531 |
Fair Value, Measurements, Recurring | Level 2 | Municipal bonds | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 6 | 506 |
Fair Value, Measurements, Recurring | Level 2 | Corporate notes | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 169 | 546 |
Fair Value, Measurements, Recurring | Level 2 | U.S. agency securities | | | |
Available-for-sale debt securities: | | | |
Total available-for-sale securities | | 0 | 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 | | 175 | 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 October 31, 2015 was $500 million and at July 31, 2015 was $500 million. See Note 6. | |