Financial Instruments and Fair Value Measurements - Contractual Maturities of Debt Investments (Detail) $ in Millions	Jul. 31, 2015 USD ($)
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 1,024
Due after one year through five years, Amortized Cost	1,804
Total, Amortized Cost	2,828
Due in one year or less, Estimated Fair Value	1,025
Due after one year through five years, Estimated Fair Value	1,805
Total, Estimated Fair Value	$ 2,830