Marketable Securities (Details) (USD $)	9 Months Ended		12 Months Ended
	Oct. 26, 2014	Oct. 27, 2013	Jan. 26, 2014
Summary of cash equivalents and marketable securities:
Realized Investment Gains (Losses)		$ 1,800,000
Available-for-sale Securities, Amortized Cost Basis	3,984,484,000		4,087,893,000
Unrealized Gain	11,980,000		7,178,000
Unrealized Loss	(1,572,000)		(2,423,000)
Estimated Fair Value	3,994,892,000		4,092,648,000
Classified as:
Cash equivalents	148,778,000		572,425,000
Marketable securities	3,846,114,000		3,520,223,000
Total cash equivalents and marketable securities	3,994,892,000		4,092,648,000
Amortized Cost
Less than one year	1,378,709,000		1,883,132,000
Due in 1-5 years	2,490,537,000		2,114,289,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	115,238,000		90,472,000
Total	3,984,484,000		4,087,893,000
Estimated Fair Value
Less than one year	1,379,705,000		1,883,753,000
Due in 1-5 years	2,497,644,000		2,117,387,000
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	117,543,000		91,508,000
Total	3,994,892,000		4,092,648,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,306,824,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,615,187,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,922,011,000
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(184,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(1,388,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(1,572,000)
Corporate debt securities
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	1,954,162,000		1,762,833,000
Unrealized Gain	3,418,000		1,837,000
Unrealized Loss	(520,000)		(945,000)
Estimated Fair Value	1,957,060,000		1,763,725,000
Classified as:
Total cash equivalents and marketable securities	1,957,060,000		1,763,725,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	698,851,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,258,209,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,957,060,000
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(83,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(437,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(520,000)
Debt securities of United States government agencies
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	585,391,000		1,012,740,000
Unrealized Gain	787,000		848,000
Unrealized Loss	(53,000)		(261,000)
Estimated Fair Value	586,125,000		1,013,327,000
Classified as:
Total cash equivalents and marketable securities	586,125,000		1,013,327,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	278,703,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	307,422,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	586,125,000
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(8,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(45,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(53,000)
Debt securities issued by United States Treasury
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	575,188,000		495,889,000
Unrealized Gain	2,891,000		621,000
Unrealized Loss	(66,000)		(57,000)
Estimated Fair Value	578,013,000		496,453,000
Classified as:
Total cash equivalents and marketable securities	578,013,000		496,453,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	71,564,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	506,449,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	578,013,000
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(66,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(66,000)
Asset-backed Securities
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	437,791,000		258,017,000
Unrealized Gain	159,000		15,000
Unrealized Loss	(199,000)		(315,000)
Estimated Fair Value	437,751,000		257,717,000
Classified as:
Total cash equivalents and marketable securities	437,751,000		257,717,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	224,100,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	213,651,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	437,751,000
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(27,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(173,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(200,000)
Mortgage backed securities issued by United Sates government-sponsored enterprises
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	273,812,000		185,594,000
Unrealized Gain	4,590,000		3,837,000
Unrealized Loss	(718,000)		(725,000)
Estimated Fair Value	277,684,000		188,706,000
Classified as:
Total cash equivalents and marketable securities	277,684,000		188,706,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	277,684,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	277,684,000
Unrealized Loss Position, Aggregate Losses
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	(717,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(717,000)
Foreign government bonds
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	85,259,000		64,955,000
Unrealized Gain	135,000		20,000
Unrealized Loss	(16,000)		(120,000)
Estimated Fair Value	85,378,000		64,855,000
Classified as:
Total cash equivalents and marketable securities	85,378,000		64,855,000
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	33,606,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	51,772,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	85,378,000
Unrealized Loss Position, Aggregate Losses
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	(16,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(16,000)
Money market funds
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	72,881,000		307,865,000
Unrealized Gain	0		0
Unrealized Loss	0		0
Estimated Fair Value	72,881,000		307,865,000
Classified as:
Total cash equivalents and marketable securities	$ 72,881,000		$ 307,865,000