Fair Value of Financial Assets and Liabilities (Details) (USD $)	Oct. 26, 2014		Jan. 26, 2014
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 3,994,892,000		$ 4,092,648,000
Cash equivalents of corporate debt securities	75,900,000
Marketable securities of corporate debt securities	1,880,000,000
Debt Instrument, Face Amount	1,500,000,000		1,500,000,000
Convertible Debt, Fair Value Disclosures	1,700,000,000		1,530,000,000
Estimate of Fair Value
Financial assets and liabilities measured at fair value:
Total cash equivalents and marketable securities	3,994,892,000
Quoted Price in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value:
Money market funds	72,881,000	[1]
Total cash equivalents and marketable securities	72,881,000
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value:
Corporate debt securities	1,957,060,000	[2]
Debt securities issued by US Government agencies	586,125,000
Debt securities issued by United States Treasury	578,013,000	[3]
Asset-backed securities	437,751,000
Mortgage-backed securities issued by government-sponsored agencies	277,684,000	[3]
Foreign government bonds	85,378,000	[3]
Money market funds	0
Total cash equivalents and marketable securities	3,922,011,000
Corporate debt securities
Financial assets and liabilities measured at fair value:
Estimated Fair Value	1,957,060,000		1,763,725,000
Debt securities of United States government agencies
Financial assets and liabilities measured at fair value:
Estimated Fair Value	586,125,000		1,013,327,000
Debt securities issued by United States Treasury
Financial assets and liabilities measured at fair value:
Estimated Fair Value	578,013,000		496,453,000
Asset-backed Securities
Financial assets and liabilities measured at fair value:
Estimated Fair Value	437,751,000		257,717,000
Mortgage backed securities issued by United Sates government-sponsored enterprises
Financial assets and liabilities measured at fair value:
Estimated Fair Value	277,684,000		188,706,000
Foreign government bonds
Financial assets and liabilities measured at fair value:
Estimated Fair Value	85,378,000		64,855,000
Money market funds
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 72,881,000		$ 307,865,000

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

[2] Includes $75.9 million in cash equivalents and $1.88 billion in marketable securities on the Condensed Consolidated Balance Sheets.

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