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Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
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Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | $ 104,246 | $ 162,942
Fair Value, Measurements, Recurring |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 104,246 | 162,942
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 45,839 | 83,092
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 58,407 | 79,850
Fair Value, Measurements, Recurring | US Government |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 42,551 | 66,094
Fair Value, Measurements, Recurring | US Government | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 42,551 | 66,094
Fair Value, Measurements, Recurring | Corporate Bonds |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 37,080 | 68,084
Fair Value, Measurements, Recurring | Corporate Bonds | Significant Other Observable Inputs (Level 2) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 37,080 | 68,084
Fair Value, Measurements, Recurring | Commercial Paper |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 19,696 | 7,658
Fair Value, Measurements, Recurring | Commercial Paper | Significant Other Observable Inputs (Level 2) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 19,696 | 7,658
Fair Value, Measurements, Recurring | Money Market Funds |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 3,288 | 16,998
Fair Value, Measurements, Recurring | Money Market Funds | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 3,288 | 16,998
Fair Value, Measurements, Recurring | Certificates of Deposit |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | 1,631 | 4,108
Fair Value, Measurements, Recurring | Certificates of Deposit | Significant Other Observable Inputs (Level 2) |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Marketable securities: | $ 1,631 | $ 4,108

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