Marketable Securities (Details) (USD $)	3 Months Ended		9 Months Ended
	Oct. 28, 2012	Oct. 30, 2011	Oct. 28, 2012	Oct. 30, 2011	Jan. 29, 2012
Summary of cash equivalents and marketable securities:
Amortized Cost	$ 2,998,640,000		$ 2,998,640,000		$ 2,864,755,000
Unrealized Gain	12,317,000		12,317,000		11,998,000
Unrealized Loss	(546,000)		(546,000)		(487,000)
Estimated Fair Value	3,010,411,000		3,010,411,000		2,876,266,000
Classified as:
Cash equivalents	101,027,000		101,027,000		414,566,000
Marketable securities	2,909,384,000		2,909,384,000		2,461,700,000
Total cash equivalents and marketable securities	3,010,411,000		3,010,411,000		2,876,266,000
Amortized Cost
Less than one year	1,301,359,000		1,301,359,000		1,705,916,000
Due in 1-5 years	1,582,124,000		1,582,124,000		1,047,956,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	115,157,000		115,157,000		110,883,000
Total	2,998,640,000		2,998,640,000		2,864,755,000
Estimated Fair Value
Less than one year	1,303,269,000		1,303,269,000		1,708,154,000
Due in 1-5 years	1,588,451,000		1,588,451,000		1,053,265,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	118,691,000		118,691,000		114,847,000
Total	3,010,411,000		3,010,411,000		2,876,266,000
Net realized gain	100,000	100,000	400,000	500,000
Debt securities of United States government agencies
Summary of cash equivalents and marketable securities:
Amortized Cost	846,587,000		846,587,000		769,300,000
Unrealized Gain	1,175,000		1,175,000		1,605,000
Unrealized Loss	(166,000)		(166,000)		(151,000)
Estimated Fair Value	847,596,000		847,596,000		770,754,000
Classified as:
Total cash equivalents and marketable securities	847,596,000		847,596,000		770,754,000
Corporate debt securities
Summary of cash equivalents and marketable securities:
Amortized Cost	1,187,944,000		1,187,944,000		1,114,439,000
Unrealized Gain	3,841,000		3,841,000		3,268,000
Unrealized Loss	(127,000)		(127,000)		(260,000)
Estimated Fair Value	1,191,658,000		1,191,658,000		1,117,447,000
Classified as:
Total cash equivalents and marketable securities	1,191,658,000		1,191,658,000		1,117,447,000
Mortgage backed securities issued by United Sates government-sponsored enterprises
Summary of cash equivalents and marketable securities:
Amortized Cost	184,488,000		184,488,000		156,668,000
Unrealized Gain	6,321,000		6,321,000		4,964,000
Unrealized Loss	(148,000)		(148,000)		(73,000)
Estimated Fair Value	190,661,000		190,661,000		161,559,000
Classified as:
Total cash equivalents and marketable securities	190,661,000		190,661,000		161,559,000
Money market funds
Summary of cash equivalents and marketable securities:
Amortized Cost	85,030,000		85,030,000		290,732,000
Unrealized Gain	0		0		0
Unrealized Loss	0		0		0
Estimated Fair Value	85,030,000		85,030,000		290,732,000
Classified as:
Total cash equivalents and marketable securities	85,030,000		85,030,000		290,732,000
Debt securities issued by United States Treasury
Summary of cash equivalents and marketable securities:
Amortized Cost	694,591,000		694,591,000		533,616,000
Unrealized Gain	980,000		980,000		2,161,000
Unrealized Loss	(105,000)		(105,000)		(3,000)
Estimated Fair Value	695,466,000		695,466,000		535,774,000
Classified as:
Total cash equivalents and marketable securities	$ 695,466,000		$ 695,466,000		$ 535,774,000