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Cash Equivalents and Marketable Securities - Schedule of Fair Value and Amortized Cost of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Marketable Securities [Line Items] |  |
Amortized Cost | $ 915,840 | $ 669,831
Gross Unrealized Gains | 72 | 268
Gross Unrealized Losses | (137) | (12)
Fair Value | 915,775 | 670,087
Short-term Marketable Securities [Member] |  |
Marketable Securities [Line Items] |  |
Fair Value | 225,417 | 472,213
Long-term Marketable Securities [Member] |  |
Marketable Securities [Line Items] |  |
Fair Value | 317,511 | 79,995
U.S. Treasury Securities [Member] |  |
Marketable Securities [Line Items] |  |
Amortized Cost | 249,817 | 202,674
Gross Unrealized Gains | 41 | 27
Gross Unrealized Losses | (97) |
Fair Value | 249,761 | 202,701
U.S. Government Agency Securities [Member] |  |
Marketable Securities [Line Items] |  |
Amortized Cost | 103,950 | 205,558
Gross Unrealized Gains | 25 | 207
Gross Unrealized Losses | (14) | (1)
Fair Value | 103,961 | 205,764
Corporate Debt Securities [Member] |  |
Marketable Securities [Line Items] |  |
Amortized Cost | 230,724 | 211,086
Gross Unrealized Gains | 6 | 34
Gross Unrealized Losses | (26) | (11)
Fair Value | 230,704 | 211,109
Money Market Funds [Member] |  |
Marketable Securities [Line Items] |  |
Amortized Cost | 331,349 | 50,513
Fair Value | 331,349 | 50,513
Cash Equivalents [Member] |  |
Marketable Securities [Line Items] |  |
Fair Value | $ 372,847 | $ 117,879

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