| Fair Value Measurements |
8. Fair Value Measurements
Assets and liabilities measured at fair value are classified into the following categories:
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• |
Level 1: Quoted market prices in active markets for identical assets or liabilities. |
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• |
Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data. |
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Level 3: Unobservable inputs reflecting the reporting entity’s own assumptions or external inputs from inactive markets. |
We classify our cash equivalents and marketable securities within Level 1 or Level 2 because we use quoted market prices or alternative pricing sources and models utilizing market observable inputs to determine their fair value. There were no transfers between levels during the periods presented.
The following table sets forth our financial assets as of December 31, 2018 and 2017 that are measured at fair value on a recurring basis during the period:
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December 31, 2018 |
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|
Cost or
Amortized Cost |
|
|
Gross
Unrealized
Gains |
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|
Gross
Unrealized
Losses |
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|
Total Estimated
Fair Value |
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|
(in thousands) |
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|
Cash |
$ |
279,950 |
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|
$ |
— |
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|
$ |
— |
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|
$ |
279,950 |
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Level 1 securities: |
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|
|
|
|
|
|
|
|
|
|
|
|
|
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U.S. government securities |
|
735,988 |
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|
|
12 |
|
|
|
(175 |
) |
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|
735,825 |
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U.S. government agency securities |
|
181,032 |
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|
|
4 |
|
|
|
(36 |
) |
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|
181,000 |
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Level 2 securities: |
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
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Corporate debt securities |
|
35,819 |
|
|
|
1 |
|
|
|
(18 |
) |
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35,802 |
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Commercial paper |
|
33,193 |
|
|
|
— |
|
|
|
— |
|
|
|
33,193 |
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Certificates of deposit |
|
13,293 |
|
|
|
— |
|
|
|
— |
|
|
|
13,293 |
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|
Total |
$ |
1,279,275 |
|
|
$ |
17 |
|
|
$ |
(229 |
) |
|
$ |
1,279,063 |
|
|
|
December 31, 2017 |
|
|
|
Cost or
Amortized Cost |
|
|
Gross
Unrealized
Gains |
|
|
Gross
Unrealized
Losses |
|
|
Total Estimated
Fair Value |
|
|
|
(in thousands) |
|
|
Cash |
$ |
267,715 |
|
|
$ |
— |
|
|
$ |
— |
|
|
$ |
267,715 |
|
|
Level 1 securities: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
U.S. government securities |
|
1,377,339 |
|
|
|
2 |
|
|
|
(899 |
) |
|
|
1,376,442 |
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|
U.S. government agency securities |
|
399,098 |
|
|
|
6 |
|
|
|
(222 |
) |
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|
398,882 |
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Level 2 securities: |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Corporate debt securities |
|
— |
|
|
|
— |
|
|
|
— |
|
|
|
— |
|
|
Commercial paper |
|
— |
|
|
|
— |
|
|
|
— |
|
|
|
— |
|
|
Certificates of deposit |
|
— |
|
|
|
— |
|
|
|
— |
|
|
|
— |
|
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Total |
$ |
2,044,152 |
|
|
$ |
8 |
|
|
$ |
(1,121 |
) |
|
$ |
2,043,039 |
|
The gross unrealized loss that had been in a continuous loss position for 12 months or longer was not material as of December 31, 2018 and 2017. As of December 31, 2018, we considered the decreases in market value on our marketable securities to be temporary in nature and did not consider any of our investments to be other-than-temporarily impaired. All of our marketable securities have contractual maturities of less than one year.
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