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Short-term Investments (Tables) | 9 Months Ended
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Sep. 30, 2021
Short Term Investments [Abstract] |
Summary of Short-term Investments | The following is a summary of our short-term investments (in thousands):
|  | September 30, 2021 |
|  |  |  |  |  | Gross |  |  | Gross |  |  |  |  |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Estimated |
|  | Cost |  |  | Gains |  |  | Losses |  |  | Fair Value |
U.S. corporate debt securities |  | $ | 4,188 |  |  | $ | — |  |  | $ | (2 | ) |  | $ | 4,186 |
Foreign corporate debt securities |  |  | 6,079 |  |  |  | — |  |  |  | (2 | ) |  |  | 6,077 |
U.S. commercial paper |  |  | 10,995 |  |  |  | — |  |  |  | — |  |  |  | 10,995 |
Foreign commercial paper |  |  | 21,992 |  |  |  | — |  |  |  | — |  |  |  | 21,992 |
Total |  | $ | 43,254 |  |  | $ | — |  |  | $ | (4 | ) |  | $ | 43,250 |
|  | December 31, 2020 |
|  |  |  |  |  | Gross |  |  | Gross |  |  |  |  |
|  | Amortized |  |  | Unrealized |  |  | Unrealized |  |  | Estimated |
|  | Cost |  |  | Gains |  |  | Losses |  |  | Fair Value |
U.S. treasury bills and government agency obligations |  | $ | 20,110 |  |  | $ | 166 |  |  | $ | — |  |  | $ | 20,276 |
U.S. corporate debt securities |  |  | 11,505 |  |  |  | 42 |  |  |  | — |  |  |  | 11,547 |
Foreign corporate debt securities |  |  | 15,508 |  |  |  | 49 |  |  |  | — |  |  |  | 15,557 |
U.S. commercial paper |  |  | 13,997 |  |  |  | — |  |  |  | — |  |  |  | 13,997 |
Foreign commercial paper |  |  | 41,976 |  |  |  | — |  |  |  | — |  |  |  | 41,976 |
Total |  | $ | 103,096 |  |  | $ | 257 |  |  | $ | — |  |  | $ | 103,353 |

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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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