Stockholders Equity - Combined Activity under Stock Option Plans and Agreements (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended
	Oct. 26, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of Shares	20.6
Options granted, Numbers of Shares	2.2
Options exercised, Number of Shares	(1.1)
Options forfeited and expired, Number of Shares	(0.6)
Ending balance, Number of Shares	21.1
Options vested and expected to vest, Number of Shares	20.5
Exercisable, Number of Shares	15.0
Beginning balance, Weighted-Average Exercise Price	$ 29.98
Options granted, Weighted-Average Exercise Price	$ 30.03
Options exercised, Weighted-Average Exercise Price	$ 18.05
Options forfeited and expired, Weighted-Average Exercise Price	$ 39.75
Ending balance, Weighted-Average Exercise Price	$ 30.31
Options vested and expected to vest, Weighted-Average Exercise Price	$ 30.07
Exercisable, Weighted-Average Exercise Price	$ 27.46
Outstanding, Weighted-Average Remaining Contractual Term	3 years 7 months 28 days
Options vested and expected to vest, Weighted-Average Remaining Contractual Term	3 years 7 months 2 days
Exercisable, Weighted-Average Remaining Contractual Term	2 years 11 months 12 days
Outstanding, Aggregate Intrinsic Value	$ 75.3
Options vested and expected to vest, Aggregate Intrinsic Value	75.2
Exercisable, Aggregate Intrinsic Value	$ 69.3