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FAIR VALUE MEASUREMENTS - SECURITY TYPE (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Included in cash and cash equivalents: |  |
Amortized Cost | $ 24,805 |
Estimated Fair Value | 24,805 |
Restricted cash: |  |
Amortized Cost | 363 | $ 363
Estimated Fair Value | 363 | 363
Marketable securities: |  |
Amortized Cost | 186,430 | 249,659
Gross Unrealized Gains | 54 | 111
Gross Unrealized Losses | (38) | (33)
Estimated Fair Value | 186,446 | 249,737
Money market funds |  |
Included in cash and cash equivalents: |  |
Amortized Cost | 19,805 | 4,356
Estimated Fair Value | 19,805 | 4,356
Restricted cash: |  |
Amortized Cost | 92 | 92
Estimated Fair Value | 92 | 92
Commercial paper |  |
Included in cash and cash equivalents: |  |
Amortized Cost | 5,000 |
Estimated Fair Value | 5,000 |
Certificate of deposit |  |
Restricted cash: |  |
Amortized Cost | 271 | 271
Estimated Fair Value | 271 | 271
U.S. Treasury securities (due in less than one year) |  |
Marketable securities: |  |
Amortized Cost | 14,056 | 5,608
Gross Unrealized Gains | 3 | 2
Estimated Fair Value | 14,059 | 5,610
U.S. Treasury securities (due in one to two years) |  |
Marketable securities: |  |
Amortized Cost | 7,099 | 5,093
Gross Unrealized Gains | 2 | 2
Estimated Fair Value | 7,101 | 5,095
Municipal securities (due in one to two years) |  |
Marketable securities: |  |
Amortized Cost | 3,000 |
Gross Unrealized Losses | (1) |
Estimated Fair Value | 2,999 |
Government-sponsored enterprise securities (due in less than one year) |  |
Marketable securities: |  |
Amortized Cost | 11,250 | 5,249
Gross Unrealized Gains | 2 | 3
Estimated Fair Value | 11,252 | 5,252
Government-sponsored enterprise securities (due in one to two years) |  |
Marketable securities: |  |
Amortized Cost | 5,000 | 23,499
Gross Unrealized Gains |  | 7
Gross Unrealized Losses | (3) | (1)
Estimated Fair Value | 4,997 | 23,505
Commercial paper (due in less than one year) |  |
Marketable securities: |  |
Amortized Cost | 72,440 | 112,388
Gross Unrealized Gains | 10 | 29
Gross Unrealized Losses | (10) | (8)
Estimated Fair Value | 72,440 | 112,409
Corporate notes (due in less than one year) |  |
Marketable securities: |  |
Amortized Cost | 49,309 | 63,051
Gross Unrealized Gains | 32 | 35
Gross Unrealized Losses | (8) | (7)
Estimated Fair Value | 49,333 | 63,079
Corporate notes (due in one to two years) |  |
Marketable securities: |  |
Amortized Cost | 24,276 | 34,771
Gross Unrealized Gains | 5 | 33
Gross Unrealized Losses | (16) | (17)
Estimated Fair Value | $ 24,265 | $ 34,787

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