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Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Money Market Funds | Level 1 |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cash equivalents and marketable securities, Amortized Cost | $ 37,951 | $ 61,104
Cash equivalents and marketable securities, Fair Market Value | 37,951 | 61,104
U.S Government Treasury Securities | Level 1 |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cash equivalents and marketable securities, Amortized Cost | 357,725 | 227,446
Cash equivalents and marketable securities, Unrealized Gains | 620 | 149
Cash equivalents and marketable securities, Unrealized Losses | (6) | (8)
Cash equivalents and marketable securities, Fair Market Value | 358,339 | 227,587
Corporate Bonds | Level 2 |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cash equivalents and marketable securities, Amortized Cost | 5,000 | 10,103
Cash equivalents and marketable securities, Unrealized Gains |  | 3
Cash equivalents and marketable securities, Unrealized Losses |  | (2)
Cash equivalents and marketable securities, Fair Market Value | 5,000 | 10,104
Cash Equivalents and Marketable Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cash equivalents and marketable securities, Amortized Cost | 400,676 | 342,388
Cash equivalents and marketable securities, Unrealized Gains | 620 | 152
Cash equivalents and marketable securities, Unrealized Losses | (6) | (10)
Cash equivalents and marketable securities, Fair Market Value | $ 401,290 | 342,530
Commercial Paper | Level 2 |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cash equivalents and marketable securities, Amortized Cost |  | 43,735
Cash equivalents and marketable securities, Fair Market Value |  | $ 43,735

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- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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