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Cash Equivalents and Marketable Securities - Schedule of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019 | Sep. 30, 2019
--- | --- | --- | ---
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | $ 201,646 | $ 131,499 |
Unrealized Gains | 237 | 168 |
Unrealized (Losses) | 0 | (3) |
Fair Value | 201,883 | 131,664 |
Less amounts classified as cash equivalents, Amortized Cost Basis | (64,370) | (4,960) | $ (11,954)
Marketable Securities |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | 137,753 | 128,348 |
Unrealized Gains | 237 | 168 |
Unrealized (Losses) | 0 | (3) |
Fair Value | 137,990 | 128,513 |
Cash Equivalents |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Less amounts classified as cash equivalents, Amortized Cost Basis | (63,893) | (3,151) |
Less amounts classified as cash equivalents, Fair Value | (63,893) | (3,151) |
Money Market Funds |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | 63,893 | 3,151 |
Unrealized Gains | 0 | 0 |
Unrealized (Losses) | 0 | 0 |
Fair Value | 63,893 | 3,151 |
Commercial Paper |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | 40,182 | 4,952 |
Unrealized Gains | 0 | 0 |
Unrealized (Losses) | 0 | 0 |
Fair Value | 40,182 | 4,952 |
Corporate Debt Securities |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | 42,399 | 69,423 |
Unrealized Gains | 81 | 79 |
Unrealized (Losses) | 0 | (3) |
Fair Value | 42,480 | 69,499 |
Asset-backed Securities |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | 8,573 | 27,005 |
Unrealized Gains | 74 | 50 |
Unrealized (Losses) | 0 | 0 |
Fair Value | 8,647 | 27,055 |
U.S. Government Agencies |  |  |
Cash And Cash Equivalents [Line Items] |  |  |
Amortized Cost Basis | 46,599 | 26,968 |
Unrealized Gains | 82 | 39 |
Unrealized (Losses) | 0 | 0 |
Fair Value | $ 46,681 | $ 27,007 |

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