Fair Value of Financial Assets and Liabilities (Details) (USD $)	Jul. 27, 2014		Jan. 26, 2014
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 4,123,343,000		$ 4,092,648,000
Cash equivalents of corporate debt securities	96,200,000
Marketable securities of corporate debt securities	1,950,000,000
Cash equivalents of US Govt Agencies Debt Securities	36,700,000
Marketable Securities of US Govt Agencies Debt Securities	663,500,000
Debt Instrument, Face Amount	1,500,000,000		1,500,000,000
Convertible Debt, Fair Value Disclosures	1,630,000,000		1,530,000,000
Estimate of Fair Value
Financial assets and liabilities measured at fair value:
Total cash equivalents and marketable securities	4,123,343,000
Quoted Price in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value:
Money market funds	119,491,000	[1]
Total cash equivalents and marketable securities	119,491,000
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value:
Corporate debt securities	2,043,430,000	[2]
Debt securities issued by US Government agencies	700,161,000	[3]
Debt securities issued by United States Treasury	587,311,000	[4]
Asset backed securities	411,528,000	[3]
Mortgage-backed securitieis issued by Government-sponsored entities	261,422,000	[4]
Money market funds	0
Total cash equivalents and marketable securities	4,003,852,000
Corporate Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	2,043,430,000		1,828,580,000
US Government Agencies Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	700,161,000		1,013,327,000
US Treasury Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	587,311,000		496,453,000
Asset-backed Securities
Financial assets and liabilities measured at fair value:
Estimated Fair Value	411,528,000		257,717,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	261,422,000		188,706,000
Money Market Funds [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 119,491,000		$ 307,865,000

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

[2] Includes $96.2 million in cash equivalents and $1.95 billion in marketable securities on the Condensed Consolidated Balance Sheet.

[3] Includes $36.7 million in cash equivalents and $663.5 million in marketable securities on the Condensed Consolidated Balance Sheet.

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