Fair Value of Cash Equivalents and Marketable Securities (Details) (USD $)	Jul. 29, 2012		Jan. 29, 2012
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 2,886,839,000		$ 2,876,266,000
Cash equivalents of corporate debt securities	38,200,000
Marketable securities of corporate debt securities	1,174,600,000
Estimate of Fair Value
Financial assets and liabilities measured at fair value:
Total cash equivalents and marketable securities	2,886,839,000
Quoted Price in Active Markets for Identical Assets (Level 1)
Financial assets and liabilities measured at fair value:
Money market funds	70,110,000	[1]
Total cash equivalents and marketable securities	70,110,000
Significant Other Observable Inputs (Level 2)
Financial assets and liabilities measured at fair value:
Debt securities issued by US Government agencies	789,433,000	[2]
Debt securities issued by United States Treasury	631,882,000	[2]
Corporate debt securities	1,212,784,000	[3]
Mortgage-backed securitieis issued by Government-sponsored entities	182,630,000	[2]
Money market funds	0
Total cash equivalents and marketable securities	2,816,729,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	182,630,000		161,559,000
Money Market Funds [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	70,110,000		290,732,000
US Government Agencies Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	789,433,000		770,754,000
US Treasury Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	631,882,000		535,774,000
Corporate Debt Securities [Member]
Financial assets and liabilities measured at fair value:
Estimated Fair Value	$ 1,212,784,000		$ 1,117,447,000

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

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

[3] Includes $38.2 million in Cash Equivalents and $1,174.6 million in Marketable Securities on the Condensed Consolidated Balance Sheet.