Stockholders' Equity - Activity Related to Stock Options (Detail) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended
	Jan. 29, 2016 USD ($) $ / shares shares
Number of Shares
Beginning balance, Number of Shares | shares	12
Options exercised, Number of Shares | shares	(1)
Options forfeited and expired, Number of Shares | shares	(3)
Ending balance, Number of Shares | shares	8
Options vested and expected to vest, Number of Shares | shares	8
Options Exercisable, Number of Shares | shares	7
Weighted-Average Exercise Price
Beginning balance, Weighted-Average Exercise Price | $ / shares	$ 37.74
Options exercised, Weighted-Average Exercise Price | $ / shares	21.15
Options forfeited and expired, Weighted-Average Exercise Price | $ / shares	39.11
Ending balance, Weighted-Average Exercise Price | $ / shares	39.68
Options vested and expected to vest, Weighted-Average Exercise Price | $ / shares	39.73
Options Exercisable, Weighted-Average Exercise Price | $ / shares	$ 40.29
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Outstanding, Weighted-Average Remaining Contractual Term	2 years 7 months 21 days
Options vested and expected to vest, Weighted-Average Remaining Contractual Term	2 years 6 months 18 days
Exercisable, Weighted-Average Remaining Contractual Term	2 years 2 months 1 day
Outstanding, Aggregate Intrinsic Value | $	$ 1
Options vested and expected to vest, Aggregate Intrinsic Value | $	1
Exercisable, Aggregate Intrinsic Value | $	$ 1