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 |