Marketable Securities (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2011	Aug. 01, 2010	Jul. 31, 2011	Aug. 01, 2010	Jan. 30, 2011
Summary of cash equivalents and marketable securities:
Amortized Cost	$ 2,115,943,000		$ 2,115,943,000		$ 2,165,536,000
Unrealized Gain			15,294,000		10,926,000
Unrealized Loss			(162,000)		(473,000)
Estimated Fair Value	2,131,075,000		2,131,075,000		2,175,989,000
Classified as:
Cash equivalents	189,193,000		189,193,000		350,787,000
Marketable securities	1,941,882,000		1,941,882,000		1,825,202,000
Total cash equivalents and marketable securities	2,131,075,000		2,131,075,000		2,175,989,000
Amortized Cost
Less than one year	906,854,000		906,854,000		1,176,046,000
Due in 1-5 years	1,106,716,000		1,106,716,000		899,993,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	102,373,000		102,373,000		89,497,000
Total	2,115,943,000		2,115,943,000		2,165,536,000
Estimated Fair Value
Less than one year	911,822,000		911,822,000		1,178,733,000
Due in 1-5 years	1,113,855,000		1,113,855,000		904,926,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	105,398,000		105,398,000		92,330,000
Total	2,131,075,000		2,131,075,000		2,175,989,000
Net realized gain	300,000.0	700,000.0	400,000.0	1,000,000.0
Debt securities of United States government agencies
Summary of cash equivalents and marketable securities:
Amortized Cost	475,277,000		475,277,000		531,789,000
Unrealized Gain			1,196,000		1,034,000
Unrealized Loss			(53,000)		(226,000)
Estimated Fair Value	476,420,000		476,420,000		532,597,000
Classified as:
Total cash equivalents and marketable securities	476,420,000		476,420,000		532,597,000
Debt securities issued by United States Treasury
Summary of cash equivalents and marketable securities:
Amortized Cost	457,664,000		457,664,000		435,091,000
Unrealized Gain			5,842,000		1,939,000
Unrealized Loss			(12,000)		(18,000)
Estimated Fair Value	463,494,000		463,494,000		437,012,000
Classified as:
Total cash equivalents and marketable securities	463,494,000		463,494,000		437,012,000
Corporate debt securities
Summary of cash equivalents and marketable securities:
Amortized Cost	957,718,000		957,718,000		925,226,000
Unrealized Gain			3,669,000		3,354,000
Unrealized Loss			(51,000)		(208,000)
Estimated Fair Value	961,336,000		961,336,000		928,372,000
Classified as:
Total cash equivalents and marketable securities	961,336,000		961,336,000		928,372,000
Mortgage backed securities issued by United Sates government-sponsored enterprises
Summary of cash equivalents and marketable securities:
Amortized Cost	146,833,000		146,833,000		140,844,000
Unrealized Gain			4,587,000		4,599,000
Unrealized Loss			(46,000)		(21,000)
Estimated Fair Value	151,374,000		151,374,000		145,422,000
Classified as:
Total cash equivalents and marketable securities	151,374,000		151,374,000		145,422,000
Money market funds
Summary of cash equivalents and marketable securities:
Amortized Cost	78,451,000		78,451,000		132,586,000
Unrealized Gain			0		0
Unrealized Loss			0		0
Estimated Fair Value	78,451,000		78,451,000		132,586,000
Classified as:
Total cash equivalents and marketable securities	$ 78,451,000		$ 78,451,000		$ 132,586,000