Stockholders Equity - Combined Activity under Stock Option Plans and Agreements (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	9 Months Ended
	Jan. 25, 2013
Number of Shares
Beginning balance, Number of Shares	20.6
Options granted, Numbers of Shares	2.4
Options exercised, Number of Shares	(2.0)
Options forfeited and expired, Number of Shares	(0.7)
Ending balance, Number of Shares	20.3
Options vested and expected to vest, Number of Shares	19.7
Exercisable, Number of Shares	15.0
Weighted-Average Exercise Price
Beginning balance, Weighted-Average Exercise Price	$ 29.98
Options granted, Weighted-Average Exercise Price	$ 28.75
Options exercised, Weighted-Average Exercise Price	$ 17.43
Options forfeited and expired, Weighted-Average Exercise Price	$ 39.64
Ending balance, Weighted-Average Exercise Price	$ 30.74
Options vested and expected to vest, Weighted-Average Exercise Price	$ 30.56
Exercisable, Weighted-Average Exercise Price	$ 28.23
Weighted-Average Remaining Contractual Term (Years)
Outstanding, Weighted-Average Remaining Contractual Term	3 years 6 months 11 days
Options vested and expected to vest, Weighted-Average Remaining Contractual Term	3 years 5 months 19 days
Exercisable, Weighted-Average Remaining Contractual Term	2 years 10 months 17 days
Aggregate Intrinsic Value
Outstanding, Aggregate Intrinsic Value	$ 166.1
Options vested and expected to vest, Aggregate Intrinsic Value	164.1
Exercisable, Aggregate Intrinsic Value	$ 145.7