Marketable Securities (Details) (USD $)	3 Months Ended		6 Months Ended
	Jul. 29, 2012	Jul. 31, 2011	Jul. 29, 2012	Jul. 31, 2011	Jan. 29, 2012
Summary of cash equivalents and marketable securities:
Amortized Cost	$ 2,874,658,000		$ 2,874,658,000		$ 2,864,755,000
Unrealized Gain	12,547,000		12,547,000		11,998,000
Unrealized Loss	(366,000)		(366,000)		(487,000)
Estimated Fair Value	2,886,839,000		2,886,839,000		2,876,266,000
Classified as:
Cash equivalents	108,357,000		108,357,000		414,566,000
Marketable securities	2,778,482,000		2,778,482,000		2,461,700,000
Total cash equivalents and marketable securities	2,886,839,000		2,886,839,000		2,876,266,000
Amortized Cost
Less than one year	1,201,750,000		1,201,750,000		1,705,916,000
Due in 1-5 years	1,481,638,000		1,481,638,000		1,047,956,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	191,270,000		191,270,000		110,883,000
Total	2,874,658,000		2,874,658,000		2,864,755,000
Estimated Fair Value
Less than one year	1,203,585,000		1,203,585,000		1,708,154,000
Due in 1-5 years	1,487,704,000		1,487,704,000		1,053,265,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	195,550,000		195,550,000		114,847,000
Total	2,886,839,000		2,886,839,000		2,876,266,000
Net realized gain	200,000	300,000	300,000	400,000
Debt securities of United States government agencies
Summary of cash equivalents and marketable securities:
Amortized Cost	788,140,000		788,140,000		769,300,000
Unrealized Gain	1,370,000		1,370,000		1,605,000
Unrealized Loss	(77,000)		(77,000)		(151,000)
Estimated Fair Value	789,433,000		789,433,000		770,754,000
Classified as:
Total cash equivalents and marketable securities	789,433,000		789,433,000		770,754,000
Debt securities issued by United States Treasury
Summary of cash equivalents and marketable securities:
Amortized Cost	630,696,000		630,696,000		533,616,000
Unrealized Gain	1,350,000		1,350,000		2,161,000
Unrealized Loss	(164,000)		(164,000)		(3,000)
Estimated Fair Value	631,882,000		631,882,000		535,774,000
Classified as:
Total cash equivalents and marketable securities	631,882,000		631,882,000		535,774,000
Corporate debt securities
Summary of cash equivalents and marketable securities:
Amortized Cost	1,209,149,000		1,209,149,000		1,114,439,000
Unrealized Gain	3,706,000		3,706,000		3,268,000
Unrealized Loss	(71,000)		(71,000)		(260,000)
Estimated Fair Value	1,212,784,000		1,212,784,000		1,117,447,000
Classified as:
Total cash equivalents and marketable securities	1,212,784,000		1,212,784,000		1,117,447,000
Mortgage backed securities issued by United Sates government-sponsored enterprises
Summary of cash equivalents and marketable securities:
Amortized Cost	176,563,000		176,563,000		156,668,000
Unrealized Gain	6,121,000		6,121,000		4,964,000
Unrealized Loss	(54,000)		(54,000)		(73,000)
Estimated Fair Value	182,630,000		182,630,000		161,559,000
Classified as:
Total cash equivalents and marketable securities	182,630,000		182,630,000		161,559,000
Money market funds
Summary of cash equivalents and marketable securities:
Amortized Cost	70,110,000		70,110,000		290,732,000
Unrealized Gain	0		0		0
Unrealized Loss	0		0		0
Estimated Fair Value	70,110,000		70,110,000		290,732,000
Classified as:
Total cash equivalents and marketable securities	$ 70,110,000		$ 70,110,000		$ 290,732,000