Net Income per Share - Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 25, 2013	Oct. 26, 2012	Oct. 25, 2013	Oct. 26, 2012
Computation Of Earnings Per Share [Line Items]
Net income	$ 166.8	$ 109.6	$ 248.4	$ 173.4
Shares used in basic computation	340.7	362.0	345.8	364.1
Dilutive potential shares related to employee equity award plans	7.5	5.2	7.2	5.1
Dilutive impact of assumed conversion of Convertible Notes	0	1.0	1.1	0.5
Dilutive impact of warrants	0.9	0	0.4	0
Shares used in diluted computation	349.1	368.2	354.5	369.7
Basic	$ 0.49	$ 0.30	$ 0.72	$ 0.48
Diluted	$ 0.48	$ 0.30	$ 0.70	$ 0.47