Financing Arrangements - Carrying Value of Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Oct. 25, 2013	Apr. 26, 2013	Jun. 10, 2008
Debt Instrument [Line Items]
Long-term debt face amount	$ 1,000.0	$ 2,264.9
Less: Unamortized discount	(5.0)	(12.5)
Total	995.0	2,252.4
Less: Current portion	0	(1,257.8)
Total long-term portion	995.0	994.6
Senior Notes due 2017
Debt Instrument [Line Items]
Long-term debt face amount	750.0	750.0
Debt Instrument, Interest Rate, Effective Percentage	2.25%	2.25%
Senior Notes due 2022
Debt Instrument [Line Items]
Long-term debt face amount	250.0	250.0
Debt Instrument, Interest Rate, Effective Percentage	3.43%	3.43%
Convertible Notes Payable
Debt Instrument [Line Items]
Long-term debt face amount	0	1,264.9	1,265.0
Less: Unamortized discount			$ (248.0)
Debt Instrument, Interest Rate, Effective Percentage		6.31%	6.31%