| Cash Equivalents and Marketable Securities |
Cash Equivalents and Marketable SecuritiesOur cash equivalents and marketable securities related to debt securities are classified as “available-for-sale” debt securities. The following is a summary of cash equivalents and marketable securities as of January 31, 2021 and January 26, 2020: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | January 31, 2021 | | Amortized
Cost | | Unrealized
Gain | | Unrealized
Loss | | Estimated
Fair Value | | Reported as | | | | | | | Cash Equivalents | | Marketable Securities | | | | | | | | | | | | | | | (In millions) | | Corporate debt securities | $ | 4,442 | | | $ | 2 | | | $ | — | | | $ | 4,444 | | | $ | 234 | | | $ | 4,210 | | | Debt securities issued by United States government agencies | 2,975 | | | 1 | | | — | | | 2,976 | | | 28 | | | 2,948 | | | Debt securities issued by the United States Treasury | 2,846 | | | — | | | — | | | 2,846 | | | 25 | | | 2,821 | | | Certificates of deposit | 705 | | | — | | | — | | | 705 | | | 37 | | | 668 | | | Money market funds | 313 | | | — | | | — | | | 313 | | | 313 | | | — | | | Foreign government bonds | 67 | | | — | | | — | | | 67 | | | | | 67 | | | | | | | | | | | | | | | | | | | | | | | | | | | Total | $ | 11,348 | | | $ | 3 | | | $ | — | | | $ | 11,351 | | | $ | 637 | | | $ | 10,714 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | January 26, 2020 | | Amortized
Cost | | Unrealized
Gain | | Unrealized
Loss | | Estimated
Fair Value | | Reported as | | | | | | | Cash Equivalents | | Marketable Securities | | | | | | | | | | | | | | | (In millions) | | Money market funds | $ | 7,507 | | | $ | — | | | $ | — | | | $ | 7,507 | | | $ | 7,507 | | | $ | — | | | Debt securities issued by the United States Treasury | 1,358 | | | — | | | — | | | 1,358 | | | 1,358 | | | — | | | Debt securities issued by United States government agencies | 1,096 | | | — | | | — | | | 1,096 | | | 1,096 | | | — | | | Corporate debt securities | 592 | | | — | | | — | | | 592 | | | 592 | | | — | | | Foreign government bonds | 200 | | | — | | | — | | | 200 | | | 200 | | | — | | | Certificates of deposit | 27 | | | — | | | — | | | 27 | | | 27 | | | — | | | Asset-backed securities | 1 | | | — | | | — | | | 1 | | | — | | | 1 | | | | | | | | | | | | | | | Total | $ | 10,781 | | | $ | — | | | $ | — | | | $ | 10,781 | | | $ | 10,780 | | | $ | 1 | |
Net realized gains and unrealized gains and losses were not significant for all periods presented. The amortized cost and estimated fair value of cash equivalents and marketable securities as of January 31, 2021 and January 26, 2020 are shown below by contractual maturity. | | | | | | | | | | | | | | | | | | | | | | | | | | January 31, 2021 | | January 26, 2020 | | | Amortized
Cost | | Estimated
Fair Value | | Amortized
Cost | | Estimated
Fair Value | | | | | | | | | | | (In millions) | | Less than one year | $ | 10,782 | | | $ | 10,783 | | | $ | 10,781 | | | $ | 10,781 | | | Due in 1 - 5 years | 566 | | | 568 | | | — | | | — | | | | | | | | | | | Total | $ | 11,348 | | | $ | 11,351 | | | $ | 10,781 | | | $ | 10,781 | |
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