Stockholders' Equity - Activity Related to Stock Options (Detail) - Jul. 31, 2015 - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Total
Number of Shares
Beginning balance, Number of Shares	12
Options exercised, Number of Shares	(1)
Options forfeited and expired, Number of Shares	(1)
Ending balance, Number of Shares	10
Options vested and expected to vest, Number of Shares	10
Options Exercisable, Number of Shares	8
Weighted-Average Exercise Price
Beginning balance, Weighted-Average Exercise Price	$ 37.74
Options exercised, Weighted-Average Exercise Price	23.37
Options forfeited and expired, Weighted-Average Exercise Price	37.67
Ending balance, Weighted-Average Exercise Price	38.18
Options vested and expected to vest, Weighted-Average Exercise Price	38.23
Options Exercisable, Weighted-Average Exercise Price	$ 38.74
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding, Weighted-Average Remaining Contractual Term	3 years 15 days
Options vested and expected to vest, Weighted-Average Remaining Contractual Term	2 years 11 months 1 day
Exercisable, Weighted-Average Remaining Contractual Term	2 years 4 months 6 days
Outstanding, Aggregate Intrinsic Value	$ 13
Options vested and expected to vest, Aggregate Intrinsic Value	13
Exercisable, Aggregate Intrinsic Value	$ 13