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Fair Value of Financial Assets - Marketable Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Fair Value of Financial Assets and Liabilities |  |
Amortized Cost | $ 317,538 | $ 71,895
Gross Unrealized Gains | 1 | 43
Gross Unrealized Losses | (60) |
Fair Value | 317,479 | 71,938
Corporate Debt Securities and Commercial Paper |  |
Fair Value of Financial Assets and Liabilities |  |
Amortized Cost | 317,538 | 71,895
Gross Unrealized Gains | 1 | 43
Gross Unrealized Losses | (60) |
Fair Value | 317,479 | 71,938
Recurring | Estimated fair value | Corporate Debt Securities and Commercial Paper |  |
Fair Value of Financial Assets and Liabilities |  |
Fair Value | 317,479 | 71,938
Recurring | Level 2 | Estimated fair value | Corporate Debt Securities and Commercial Paper |  |
Fair Value of Financial Assets and Liabilities |  |
Fair Value | $ 317,479 | $ 71,938

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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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- Definition Amount, before tax, of unrealized loss 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 (c) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
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