Financial Instruments and Fair Value - Summary of Investments (Detail) (USD $) In Millions, unless otherwise specified	Jan. 25, 2013	Apr. 27, 2012
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	$ 5,713.8	$ 4,818.6
Gross Unrealized Gains	14.6	12.1
Gross Unrealized Losses	(4.1)	(5.5)
Estimated Fair Value	5,724.3	4,825.2
Corporate Bonds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	2,934.1	2,665.2
Gross Unrealized Gains	13.2	9.5
Gross Unrealized Losses	(1.1)	(1.4)
Estimated Fair Value	2,946.2	2,673.3
U.S. Treasury And Government Debt Securities
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	506.9	836.7
Gross Unrealized Gains	0.8	1.2
Gross Unrealized Losses	0	(0.1)
Estimated Fair Value	507.7	837.8
Commercial Paper
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	208.0	164.6
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	208.0	164.6
Certificates of Deposit
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	173.0	347.7
Gross Unrealized Gains	0.2	0.5
Gross Unrealized Losses	0	0
Estimated Fair Value	173.2	348.2
Money Market Funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	1,819.4	724.8
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	1,819.4	724.8
Auction Rate Securities
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	44.8	54.1
Gross Unrealized Gains	0.4	0.9
Gross Unrealized Losses	(3.0)	(4.0)
Estimated Fair Value	42.2	51.0
Equity Funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Cost or Amortized Cost	27.6	25.5
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 27.6	$ 25.5

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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