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Marketable Securities (Details) - USD ($) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2019 | Dec. 31, 2018
Cash equivalents |  |
Carrying Value | $ 6,294 | $ 22,858
Short-term investments |  |
Amortized Cost | 91,694 | 97,093
Unrealized Gains | 86 | 17
Unrealized Losses | 0 | (7)
Aggregate Fair Value | 91,780 | 97,103
Long-term investments |  |
Amortized Cost | 5,254 |
Unrealized Gains | 8 |
Unrealized Losses | 0 |
Aggregate Fair Value | 5,262 | 0
Total marketable securities, Amortized Cost | 103,242 | 119,951
Total marketable securities, Unrealized Gains | 94 | 17
Total marketable securities, Unrealized Losses | 0 | (7)
Total marketable securities, Aggregate Fair Value | 103,336 | 119,961
U.S. treasury securities |  |
Cash equivalents |  |
Carrying Value |  | 1,000
Short-term investments |  |
Amortized Cost | 77,526 | 65,491
Unrealized Gains | 65 | 2
Unrealized Losses | 0 | (4)
Aggregate Fair Value | 77,591 | 65,489
Corporate bonds |  |
Short-term investments |  |
Amortized Cost | 14,168 | 19,708
Unrealized Gains | 21 | 15
Unrealized Losses | 0 | (3)
Aggregate Fair Value | 14,189 | 19,720
Long-term investments |  |
Amortized Cost | 5,254 |
Unrealized Gains | 8 |
Unrealized Losses | 0 |
Aggregate Fair Value | 5,262 |
Commercial paper |  |
Cash equivalents |  |
Carrying Value |  | 6,635
Short-term investments |  |
Amortized Cost |  | 11,894
Unrealized Gains |  | 0
Unrealized Losses |  | 0
Aggregate Fair Value |  | 11,894
Money market funds |  |
Cash equivalents |  |
Carrying Value | $ 6,294 | $ 15,223
Minimum |  |
Marketable Securities [Line Items] |  |
Long-term investments, maturity (in months) | 15 months |
Maximum |  |
Marketable Securities [Line Items] |  |
Long-term investments, maturity (in months) | 17 months |

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