Financial Instruments and Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Apr. 26, 2013	Apr. 27, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 1,642.4	$ 900.0
Short-term investments	3,675.5	3,848.7
Other current assets	2.8	9.0
Other non-current assets	68.7	70.2
Total	5,389.4	4,827.9
Other current liabilities	3.1	2.6
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	1,463.1	724.8
Short-term investments	222.9	234.3
Other current assets	1.6	6.3
Other non-current assets	26.7	19.2
Total	1,714.3	984.6
Other current liabilities	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	179.3	175.2
Short-term investments	3,452.6	3,614.4
Other current assets	1.2	2.7
Other non-current assets	0	0
Total	3,633.1	3,792.3
Other current liabilities	3.1	2.6
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0	0
Short-term investments	0	0
Other current assets	0	0
Other non-current assets	42.0	51.0
Total	42.0	51.0
Other current liabilities	$ 0	$ 0