Stockholders Equity - Activity Related to Stock Options (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Jul. 25, 2014
Number of Shares
Beginning balance, Number of Shares	14.5
Options granted, Number of Shares	2.0
Options exercised, Number of Shares	(0.5)
Options forfeited and expired, Number of Shares	(0.2)
Ending balance, Number of Shares	15.8
Options vested and expected to vest, Number of Shares	15.0
Options Exercisable, Number of Shares	10.4
Weighted-Average Exercise Price
Beginning balance, Weighted-Average Exercise Price	$ 34.10
Options granted, Weighted-Average Exercise Price	$ 36.29
Options exercised, Weighted-Average Exercise Price	$ 23.60
Options forfeited and expired, Weighted-Average Exercise Price	$ 41.43
Ending balance, Weighted-Average Exercise Price	$ 34.68
Options vested and expected to vest, Weighted-Average Exercise Price	$ 34.58
Options Exercisable, Weighted-Average Exercise Price	$ 33.33
Weighted-Average Remaining Contractual Term
Outstanding, Weighted-Average Remaining Contractual Term	3 years 9 months
Options vested and expected to vest, Weighted-Average Remaining Contractual Term	3 years 7 months 17 days
Exercisable, Weighted-Average Remaining Contractual Term	2 years 7 months 17 days
Aggregate Intrinsic Value
Outstanding, Aggregate Intrinsic Value	$ 93.1
Options vested and expected to vest, Aggregate Intrinsic Value	91.6
Exercisable, Aggregate Intrinsic Value	$ 81.1