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Financial Instruments (Details) $ in Thousands | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) | Dec. 31, 2018 USD ($) | Sep. 30, 2018 USD ($)
Financial Instruments |  |  |
Transfers between fair value measurement levels | $ 0 |  | $ 0
Minimum | Reverse repurchase agreements | Government Securities and Obligations |  |  |
Financial Instruments |  |  |
Percentage of investment amount to collateralized deposits value | 102 |  |
Recurring |  |  |
Financial Instruments |  |  |
Total assets | $ 38,500 | $ 33,180 |
Recurring | Level 1 |  |  |
Financial Instruments |  |  |
Total assets | 6,144 | 5,956 |
Recurring | Level 2 |  |  |
Financial Instruments |  |  |
Total assets | 32,356 | 27,224 |
Recurring | Money market funds |  |  |
Financial Instruments |  |  |
Cash and cash equivalents | 6,144 | 5,956 |
Recurring | Money market funds | Level 1 |  |  |
Financial Instruments |  |  |
Cash and cash equivalents | 6,144 | 5,956 |
Recurring | Corporate debt securities |  |  |
Financial Instruments |  |  |
Cash and cash equivalents | 7,506 | 1,948 |
Short-term investments | 1,850 | 7,276 |
Recurring | Corporate debt securities | Level 2 |  |  |
Financial Instruments |  |  |
Cash and cash equivalents | 7,506 | 1,948 |
Short-term investments | 1,850 | 7,276 |
Recurring | Reverse repurchase agreements |  |  |
Financial Instruments |  |  |
Cash and cash equivalents | 2,000 | 3,000 |
Short-term investments | 21,000 | 15,000 |
Recurring | Reverse repurchase agreements | Level 2 |  |  |
Financial Instruments |  |  |
Cash and cash equivalents | 2,000 | 3,000 |
Short-term investments | $ 21,000 | $ 15,000 |

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