Financial Instruments and Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Jul. 26, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 469.1
Short-term investments	3,287.2
Total	3,829.9
Other current liabilities	2.2
Other Current Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	3.8
Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	69.8
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	323.2
Short-term investments	207.2
Total	560.3
Other current liabilities	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	2.3
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	27.6
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	145.9
Short-term investments	3,080.0
Total	3,227.4
Other current liabilities	2.2
Significant Other Observable Inputs (Level 2) | Other Current Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	1.5
Significant Other Observable Inputs (Level 2) | Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	0
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0
Short-term investments	0
Total	42.2
Other current liabilities	0
Significant Unobservable Inputs (Level 3) | Other Current Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	0
Significant Unobservable Inputs (Level 3) | Other Noncurrent Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other assets	$ 42.2