Fair Value of Financial Assets and Liabilities (Details) (USD $)	Apr. 26, 2015		Jan. 25, 2015
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 4,446,000,000		$ 4,421,000,000
Cash equivalents of corporate debt securities	95,000,000
Cash equivalents of debt securities of US government agencies	4,000,000
Marketable securities of corporate debt securities	2,120,000,000
Marketable securities of debt securities US government agencies	965,000,000
Debt Instrument, Face Amount	1,500,000,000		1,500,000,000
Convertible Debt, Fair Value Disclosures	1,830,000,000		1,680,000,000
Estimate of Fair Value
Financial assets and liabilities measured at fair value:
Total cash equivalents and marketable securities	4,446,000,000
Quoted Price in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value:
Money market funds	19,000,000	[1]
Total cash equivalents and marketable securities	19,000,000
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value:
Corporate debt securities	2,217,000,000	[2]
Debt securities issued by US Government agencies	969,000,000	[3]
Debt securities issued by United States Treasury	416,000,000	[4]
Asset-backed securities	480,000,000	[4]
Mortgage-backed securities issued by government-sponsored agencies	264,000,000	[4]
Foreign government bonds	81,000,000	[4]
Money market funds	0
Total cash equivalents and marketable securities	4,427,000,000
Corporate debt securities
Financial assets and liabilities measured at fair value:
Estimated Fair Value	2,217,000,000		2,186,000,000
Debt securities of United States government agencies
Financial assets and liabilities measured at fair value:
Estimated Fair Value	969,000,000		750,000,000
Asset-backed Securities
Financial assets and liabilities measured at fair value:
Estimated Fair Value	480,000,000		453,000,000
Debt securities issued by United States Treasury
Financial assets and liabilities measured at fair value:
Estimated Fair Value	416,000,000		537,000,000
Mortgage backed securities issued by United Sates government-sponsored enterprises
Financial assets and liabilities measured at fair value:
Estimated Fair Value	264,000,000		278,000,000
Foreign government bonds
Financial assets and liabilities measured at fair value:
Estimated Fair Value	81,000,000		85,000,000
Money market funds
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 19,000,000		$ 132,000,000

[1] Included in cash equivalents on the Condensed Consolidated Balance Sheets.

[2] Includes $95 million in cash equivalents and $2.12 billion in marketable securities on the Condensed Consolidated Balance Sheets.

[3] Includes $4 million in cash equivalents and $965 million in marketable securities on the Condensed Consolidated Balance Sheets.

[4] Included in marketable securities on the Condensed Consolidated Balance Sheets.