Convertible Debt (Details) $ / shares in Units, shares in Millions	3 Months Ended
	Jul. 31, 2016 USD ($)	May. 01, 2016 USD ($) $ / shares shares		Apr. 26, 2015 USD ($)	Apr. 29, 2016 $ / shares	Jan. 31, 2016 USD ($)	Oct. 25, 2015 USD ($)
Debt Instrument
Document Period End Date		May 01, 2016
Debt Instrument, Face Amount		$ 1,500,000,000				$ 1,500,000,000
Debt Instrument, Interest Rate, Stated Percentage		1.00%
Initial conversion ratio		49.5958
Principal amount of Notes		$ 1,000
Initial conversion price | $ / shares		$ 20.1630
Initial dividend | $ / shares		$ 0.085
Debt Instrument, Convertible, Conversion Ratio		49.7481
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 20.1013
Debt Instrument, Convertible, Initial Liability Amount		$ 1,350,000,000
Debt Instrument, Effective Interest Rate		3.15%
Debt Instrument, Convertible, Carrying Amount of Equity Component		$ 39,000,000				39,000,000	$ 126,000,000
Purchaser's Discount of Convertible Notes		23,000,000
Initial unamortized debt discount at issuance		148,000,000
Debt Instrument, Unamortized Discount		(79,000,000)	[1]			(87,000,000)
Convertible debt		$ 1,421,000,000				1,413,000,000
Debt Instrument, Convertible, Remaining Discount Amortization Period		2 years 7 months 6 days
Coupon Interest Expense		$ 4,000,000		$ 4,000,000
Amortization of debt discount		8,000,000		7,000,000
Debt Instrument, Convertible, Interest Expense		$ 12,000,000		$ 11,000,000
Debt Instrument, Convertible, Terms of Conversion Feature		Holders may convert all or any portion of their Notes at their option at any time prior to August 1, 2018 only under the following circumstances: (1) during any fiscal quarter (and only during such fiscal quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the measurement period) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; or (3) upon the occurrence of specified corporate events. On or after August 1, 2018 to the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their Notes regardless of the foregoing conditions.
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		130.00%
Convertible short-term debt		$ 1,421,000,000				1,413,000,000
Convertible debt conversion obligation		79,000,000				$ 87,000,000
Closing stock price | $ / shares					$ 35.53
Debt Instrument, Convertible, If-converted Value in Excess of Principal		$ 1,150,000,000
Note Hedges Initial Strike Price | $ / shares		$ 20.1630
Note Hedges Strike Price | $ / shares		20.1013
Initial Warrant Strike Price | $ / shares		27.1425
Warrant Strike Price | $ / shares		$ 27.0594
Number of Shares Covered by Warrants | shares		74
Subsequent Event [Member]
Debt Instrument
Extinguishment of Debt, Amount	$ 0

[1] As of May 1, 2016, the remaining period over which the unamortized debt discount will be amortized is 2.6 years.