Fair Value of Cash Equivalents and Marketable Securities (Details) (USD $)	Apr. 27, 2014		Jan. 26, 2014
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 4,048,605,000		$ 4,092,648,000
Cash equivalents of corporate debt securities	106,600,000
Marketable securities of corporate debt securities	1,960,000,000
Estimate of Fair Value
Financial assets and liabilities measured at fair value:
Total cash equivalents and marketable securities	4,048,605,000
Quoted Price in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value:
Money market funds	103,396,000	[1]
Total cash equivalents and marketable securities	103,396,000
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value:
Debt securities issued by US Government agencies	732,731,000	[2]
Debt securities issued by United States Treasury	584,880,000	[2]
Corporate debt securities	2,067,826,000	[3]
Mortgage-backed securitieis issued by Government-sponsored entities	202,441,000	[2]
Money market funds	0
Total cash equivalents and marketable securities	3,945,209,000
Corporate Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	2,067,826,000		1,828,580,000
US Government Agencies Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	732,731,000		1,013,327,000
US Treasury Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	584,880,000		496,453,000
Asset-backed Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	357,331,000		257,717,000
Asset backed securities	357,331,000	[2]
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	202,441,000		188,706,000
Money Market Funds [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 103,396,000		$ 307,865,000

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

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

[3] Includes $106.6 million in cash equivalents and $1.96 billion in marketable securities on the Condensed Consolidated Balance Sheet.