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Short-term Investments (Tables) | 9 Months Ended
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Sep. 30, 2020
Short Term Investments [Abstract] |
Summary of Short-term Investments | The following is a summary of our short-term investments (in thousands):
|  | September 30, 2020 |
|  |  |  |  |  | Gross |  |  | Gross |  |  |  |  |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Estimated |
|  | Cost |  |  | Gains |  |  | Losses |  |  | Fair Value |
U.S. treasury bills and government agency obligations |  | $ | 70,175 |  |  | $ | 316 |  |  | $ | — |  |  | $ | 70,491 |
U.S. corporate debt securities |  |  | 25,624 |  |  |  | 110 |  |  |  | — |  |  |  | 25,734 |
Foreign corporate debt securities |  |  | 23,534 |  |  |  | 114 |  |  |  | — |  |  |  | 23,648 |
U.S. commercial paper |  |  | 14,995 |  |  |  | — |  |  |  | — |  |  |  | 14,995 |
Foreign commercial paper |  |  | 28,137 |  |  |  | — |  |  |  | — |  |  |  | 28,137 |
Total |  | $ | 162,465 |  |  | $ | 540 |  |  | $ | — |  |  | $ | 163,005 |
|  | December 31, 2019 |
|  |  |  |  |  | Gross |  |  | Gross |  |  |  |  |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Estimated |
|  | Cost |  |  | Gains |  |  | Losses |  |  | Fair Value |
U.S. treasury bills and government agency obligations |  | $ | 140,567 |  |  | $ | 59 |  |  | $ | — |  |  | $ | 140,626 |
U.S. corporate debt securities |  |  | 80,159 |  |  |  | 11 |  |  |  | — |  |  |  | 80,170 |
Foreign corporate debt securities |  |  | 23,188 |  |  |  | 15 |  |  |  | — |  |  |  | 23,203 |
U.S. commercial paper |  |  | 32,801 |  |  |  | — |  |  |  | — |  |  |  | 32,801 |
Foreign commercial paper |  |  | 42,274 |  |  |  | — |  |  |  | — |  |  |  | 42,274 |
Total |  | $ | 318,989 |  |  | $ | 85 |  |  | $ | — |  |  | $ | 319,074 |

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- Definition Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -URI http://asc.fasb.org/topic&trid=2196928 + Details
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