Fair Value of Cash Equivalents and Marketable Securities (Details) (USD $)	3 Months Ended
	Apr. 28, 2013		Jan. 27, 2013
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 3,202,878,000		$ 3,297,263,000
Cash equivalents of US gov't agencies debt securities	2,400,000
Marketable securities of US gov't agencies debt securities	1,006,700,000
Cash equivalents of corporate debt securities	9,200,000
Marketable securities of corporate debt securities	1,229,500,000
Estimate of Fair Value
Financial assets and liabilities measured at fair value:
Total cash equivalents and marketable securities	3,202,878,000
Quoted Price in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value:
Money market funds	39,350,000	[1]
Total cash equivalents and marketable securities	39,350,000
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value:
Debt securities issued by US Government agencies	1,009,074,000	[2]
Debt securities issued by United States Treasury	725,193,000	[3]
Corporate debt securities	1,238,724,000	[4]
Mortgage-backed securitieis issued by Government-sponsored entities	190,537,000	[3]
Money market funds	0
Total cash equivalents and marketable securities	3,163,528,000
US Government Agencies Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	1,009,074,000		868,147,000
US Treasury Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	725,193,000		786,225,000
Corporate Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	1,238,724,000		1,257,930,000
Money Market Funds [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	39,350,000		195,790,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 190,537,000		$ 189,171,000

[1] Included in Cash Equivalents on the Condensed Consolidated Balance Sheet.

[2] Includes $2.4 million in Cash Equivalents and $1,006.7 million in Marketable Securities on the Condensed Consolidated Balance Sheet.

[3] Included in Marketable Securities on the Condensed Consolidated Balance Sheet.

[4] Includes $9.2 million in Cash Equivalents and $1,229.5 million in Marketable Securities on the Condensed Consolidated Balance Sheet.