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Summary of Significant Accounting Policies - Summary of Fair Value Assets Measured on Recurring Basis for Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
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Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cash and cash equivalents | $ 198,037 | $ 196,634
Fair Value Measurements Recurring |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Adjusted cost | 209,086 | 240,358
Gross unrealized gains (losses) | 8 | (9)
Fair value | 209,094 | 240,349
Cash and cash equivalents | 198,037 | 196,634
Marketable securities | 11,057 | 43,715
Fair Value Measurements Recurring | Cash |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Adjusted cost | 51,560 | 33,671
Fair value | 51,560 | 33,671
Cash and cash equivalents | 51,560 | 33,671
Fair Value Measurements Recurring | Level 1 | Money Market Accounts |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Adjusted cost | 146,477 | 158,438
Fair value | 146,477 | 158,438
Cash and cash equivalents | 146,477 | 158,438
Fair Value Measurements Recurring | Level 2 | Corporate Bonds |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Adjusted cost | 2,011 | 13,629
Gross unrealized gains (losses) | 2 | (16)
Fair value | 2,013 | 13,613
Marketable securities | 2,013 | 13,613
Fair Value Measurements Recurring | Level 2 | U.S. Treasury Securities |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Adjusted cost | 9,038 | 34,620
Gross unrealized gains (losses) | 6 | 7
Fair value | 9,044 | 34,627
Cash and cash equivalents |  | 4,525
Marketable securities | $ 9,044 | $ 30,102

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- Definition Amortized cost 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/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
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