Financing Arrangements - Carrying Value of Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Oct. 24, 2014	Apr. 25, 2014
Debt Instrument [Line Items]
Long-term debt face amount	$ 1,500.0	$ 1,000.0
Less: Unamortized discount	(5.6)	(4.5)
Total long-term debt	1,494.4	995.5
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 2021
Debt Instrument [Line Items]
Long-term debt face amount	500.0	0
Debt Instrument, Interest Rate, Effective Percentage	3.54%
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%