Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Apr. 27, 2014	Jan. 26, 2014
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	$ 4,042,002	$ 4,087,893
Unrealized Gain	8,352	7,178
Unrealized Loss	(1,749)	(2,423)
Estimated Fair Value	4,048,605	4,092,648
Classified as:
Cash equivalents	209,953	572,425
Marketable securities	3,838,652	3,520,223
Total cash equivalents and marketable securities	4,048,605	4,092,648
Amortized Cost
Less than one year	1,536,890	1,883,132
Due in 1-5 years	2,379,798	2,114,289
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	125,314	90,472
Total	4,042,002	4,087,893
Estimated Fair Value
Less than one year	1,537,853	1,883,753
Due in 1-5 years	2,383,465	2,117,387
Mortgage-backed securities issued by government-sponsored enterprises not due to a single maturity date	127,287	91,508
Total	4,048,605	4,092,648
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,434,456
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,510,753
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,945,209
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(80)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(1,669)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(1,749)
Debt securities of United States government agencies
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	732,145	1,012,740
Unrealized Gain	684	848
Unrealized Loss	(98)	(261)
Estimated Fair Value	732,731	1,013,327
Classified as:
Total cash equivalents and marketable securities	732,731	1,013,327
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	408,621
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	324,110
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	732,731
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(9)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(89)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(98)
Corporate debt securities
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	2,065,847	1,827,788
Unrealized Gain	2,671	1,857
Unrealized Loss	(692)	(1,065)
Estimated Fair Value	2,067,826	1,828,580
Classified as:
Total cash equivalents and marketable securities	2,067,826	1,828,580
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	807,941
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,259,885
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,067,826
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(41)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(651)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(692)
Mortgage backed securities issued by United Sates government-sponsored enterprises
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	199,362	185,594
Unrealized Gain	3,874	3,837
Unrealized Loss	(795)	(725)
Estimated Fair Value	202,441	188,706
Classified as:
Total cash equivalents and marketable securities	202,441	188,706
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	202,441
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	202,441
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	(795)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(795)
Asset-backed Securities [Member]
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	357,216	258,017
Unrealized Gain	239	15
Unrealized Loss	(124)	(315)
Estimated Fair Value	357,331	257,717
Classified as:
Total cash equivalents and marketable securities	357,331	257,717
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	153,635
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	203,696
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	357,331
Unrealized Loss Position, Aggregate Losses
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	(30)
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	(94)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	(124)
Money market funds
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	103,396	307,865
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated Fair Value	103,396	307,865
Classified as:
Total cash equivalents and marketable securities	103,396	307,865
Debt securities issued by United States Treasury
Summary of cash equivalents and marketable securities:
Available-for-sale Securities, Amortized Cost Basis	584,036	495,889
Unrealized Gain	884	621
Unrealized Loss	(40)	(57)
Estimated Fair Value	584,880	496,453
Classified as:
Total cash equivalents and marketable securities	584,880	496,453
Unrealized Loss Position, Fair Value
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	64,259
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	520,621
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	584,880
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	(40)
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ (40)