Marketable Securities (Details) (USD $)	12 Months Ended
	Jan. 26, 2014	Jan. 27, 2013	Jan. 29, 2012
Summary of cash equivalents and marketable securities:
Amortized Cost	$ 4,087,893,000	$ 3,286,436,000
Classified as:
Cash equivalents	572,425,000	302,166,000
Marketable securities	3,520,223,000	2,995,097,000
Total cash equivalents and marketable securities	4,092,648,000	3,297,263,000
Amortized Cost Basis [Abstract]
Less than one year	1,883,132,000	1,397,350,000
Due in 1-5 years	2,114,289,000	1,777,785,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	90,472,000	111,301,000
Total	4,087,893,000	3,286,436,000
Estimated Fair Value [Abstract]
Less than one year	1,883,753,000	1,399,304,000
Due in 1-5 years	2,117,387,000	1,783,103,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	91,508,000	114,856,000
Total	4,092,648,000	3,297,263,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,575,887,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,208,896,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,784,783,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(315,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(2,108,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(2,423,000)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	8
Net realized gain	2,400,000	500,000	400,000
Available For Sale Securities Net Unrealized Gain Loss	4,800,000	10,900,000
Gross Unrealized Gain	7,178,000	11,670,000
Gross Unrealized Losses	(2,423,000)	(843,000)
US Government Agencies Debt Securities
Summary of cash equivalents and marketable securities:
Amortized Cost	1,012,740,000	867,087,000
Classified as:
Total cash equivalents and marketable securities	1,013,327,000	868,147,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	576,920,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	436,407,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,013,327,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(100,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(161,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(261,000)
Gross Unrealized Gain	848,000	1,199,000
Gross Unrealized Losses	(261,000)	(139,000)
Corporate Debt Securities
Summary of cash equivalents and marketable securities:
Amortized Cost	1,827,788,000	1,255,297,000
Classified as:
Total cash equivalents and marketable securities	1,828,580,000	1,257,930,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	789,095,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,039,485,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,828,580,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(87,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(978,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(1,065,000)
Gross Unrealized Gain	1,857,000	3,175,000
Gross Unrealized Losses	(1,065,000)	(542,000)
Mortgage backed securities issued by United Sates government-sponsored enterprises
Summary of cash equivalents and marketable securities:
Amortized Cost	185,594,000	183,034,000
Classified as:
Total cash equivalents and marketable securities	188,706,000	189,171,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	999,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	187,707,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	188,706,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(725,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(725,000)
Gross Unrealized Gain	3,837,000	6,194,000
Gross Unrealized Losses	(725,000)	(57,000)
Money Market Funds
Summary of cash equivalents and marketable securities:
Amortized Cost	307,865,000	195,790,000
Classified as:
Total cash equivalents and marketable securities	307,865,000	195,790,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Gross Unrealized Gain	0	0
Gross Unrealized Losses	0	0
US Treasury Securities
Summary of cash equivalents and marketable securities:
Amortized Cost	495,889,000	785,228,000
Classified as:
Total cash equivalents and marketable securities	496,453,000	786,225,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	88,984,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	407,469,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	496,453,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(9,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(48,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(57,000)
Gross Unrealized Gain	621,000	1,102,000
Gross Unrealized Losses	(57,000)	(105,000)
Asset-backed Securities
Summary of cash equivalents and marketable securities:
Amortized Cost	258,017,000
Classified as:
Total cash equivalents and marketable securities	257,717,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	119,889,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	137,828,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	257,717,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(119,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(196,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(315,000)
Gross Unrealized Gain	15,000
Gross Unrealized Losses	$ (315,000)