| Marketable Securities |
Marketable Securities Our cash equivalents and marketable securities are classified as “available-for-sale” debt securities. The following is a summary of cash equivalents and marketable securities as of April 28, 2019 and January 27, 2019: | | | | | | | | | | | | | | | | | | | | | | | | | | April 28, 2019 | | Amortized Cost | | Unrealized Gain | | Unrealized Loss | | Estimated Fair Value | | Reported as | | | | | | Cash Equivalents | | Marketable Securities | | (In millions) | Corporate debt securities | $ | 2,899 |
| | $ | 2 |
| | $ | (2 | ) | | $ | 2,899 |
| | $ | 1,048 |
| | $ | 1,851 |
| Debt securities of United States government agencies | 1,882 |
| | — |
| | (1 | ) | | 1,881 |
| | — |
| | 1,881 |
| Debt securities issued by the United States Treasury | 1,833 |
| | — |
| | — |
| | 1,833 |
| | 932 |
| | 901 |
| Money market funds | 681 |
| | — |
| | — |
| | 681 |
| | 681 |
| | — |
| Foreign government bonds | 183 |
| | — |
| | — |
| | 183 |
| | — |
| | 183 |
| Asset-backed securities | 133 |
| | — |
| | (1 | ) | | 132 |
| | — |
| | 132 |
| Mortgage-backed securities issued by United States government-sponsored enterprises | 81 |
| | 1 |
| | — |
| | 82 |
| | — |
| | 82 |
| Total | $ | 7,692 |
| | $ | 3 |
| | $ | (4 | ) | | $ | 7,691 |
| | $ | 2,661 |
| | $ | 5,030 |
|
| | | | | | | | | | | | | | | | | | | | | | | | | | January 27, 2019 | | Amortized
Cost | | Unrealized
Gain | | Unrealized
Loss | | Estimated
Fair Value | | Reported as | | | | | | Cash Equivalents | | Marketable Securities | | (In millions) | Corporate debt securities | $ | 2,626 |
| | $ | — |
| | $ | (6 | ) | | $ | 2,620 |
| | $ | 25 |
| | $ | 2,595 |
| Debt securities of United States government agencies | 2,284 |
| | — |
| | (4 | ) | | 2,280 |
| | — |
| | 2,280 |
| Debt securities issued by the United States Treasury | 1,493 |
| | — |
| | (1 | ) | | 1,492 |
| | 176 |
| | 1,316 |
| Money market funds | 483 |
| | — |
| | — |
| | 483 |
| | 483 |
| | — |
| Foreign government bonds | 209 |
| | — |
| | — |
| | 209 |
| | — |
| | 209 |
| Asset-backed securities | 152 |
| | — |
| | (1 | ) | | 151 |
| | — |
| | 151 |
| Mortgage-backed securities issued by United States government-sponsored enterprises | 88 |
| | 1 |
| | — |
| | 89 |
| | — |
| | 89 |
| Total | $ | 7,335 |
| | $ | 1 |
| | $ | (12 | ) | | $ | 7,324 |
| | $ | 684 |
| | $ | 6,640 |
|
The following table provides the breakdown of unrealized losses as of April 28, 2019, aggregated by investment category and length of time that individual securities have been in a continuous loss position: | | | | | | | | | | | | | | | | | | | | | | | | | | Less than 12 Months | | 12 Months or Greater | | Total | | Estimated Fair Value | | Gross Unrealized Losses | | Estimated Fair Value | | Gross Unrealized Losses | | Estimated Fair Value | | Gross Unrealized Losses | | (In millions) | Debt securities issued by United States government agencies | $ | 1,429 |
| | $ | — |
| | $ | 306 |
| | $ | (1 | ) | | $ | 1,735 |
| | $ | (1 | ) | Corporate debt securities | 330 |
| | (1 | ) | | 453 |
| | (1 | ) | | 783 |
| | (2 | ) | Asset-backed securities | — |
| | — |
| | 132 |
| | (1 | ) | | 132 |
| | (1 | ) | Total | $ | 1,759 |
| | $ | (1 | ) | | $ | 891 |
| | $ | (3 | ) | | $ | 2,650 |
| | $ | (4 | ) |
The gross unrealized losses are related to fixed income securities, temporary in nature, and driven primarily by changes in interest rates. We have the intent and ability to hold our investments until maturity. For the first quarter of fiscal years 2020 and 2019, there were no other-than-temporary impairment losses and net realized gains were not significant. The amortized cost and estimated fair value of cash equivalents and marketable securities as of April 28, 2019 and January 27, 2019 are shown below by contractual maturity. | | | | | | | | | | | | | | | | | | April 28, 2019 | | January 27, 2019 | | Amortized Cost | | Estimated Fair Value | | Amortized Cost | | Estimated Fair Value | | (In millions) | Less than 1 year | $ | 5,773 |
| | $ | 5,770 |
| | $ | 5,042 |
| | $ | 5,034 |
| Due in 1 - 5 years | 1,896 |
| | 1,898 |
| | 2,271 |
| | 2,268 |
| Mortgage-backed securities issued by United States government-sponsored enterprises not due at a single maturity date | 23 |
| | 23 |
| | 22 |
| | 22 |
| Total | $ | 7,692 |
| | $ | 7,691 |
| | $ | 7,335 |
| | $ | 7,324 |
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