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Other Investments, Short-term (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Short-term investments |  |
Short-term investments amortized cost basis | $ 6,997 | $ 15,144
Minimum period for maturity dates for short-term investments | 90 days |

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- Definition Minimum period for maturity dates relating to short-term investments, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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