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. 26, 2012	Oct. 28, 2011	Oct. 26, 2012	Oct. 28, 2011
Computation Of Earnings Per Share [Line Items]
Net income	$ 109.6	$ 165.6	$ 173.4	$ 305.1
Shares used in basic computation	362.0	361.5	364.1	365.9
Dilutive potential shares related to employee equity award plans	5.2	7.8	5.1	9.8
Dilutive impact of assumed conversion of Notes	1.0	6.7	0.5	11.1
Dilutive impact of warrants	0	0	0	4.0
Shares used in diluted computation	368.2	376.0	369.7	390.8
Basic	$ 0.30	$ 0.46	$ 0.48	$ 0.83
Diluted	$ 0.30	$ 0.44	$ 0.47	$ 0.78