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Financial Instruments (Details Textual) | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2016 | Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract] |  |
Overnight reverse repurchase agreements, percent of total assets | 0.30% | 0.70%
Average maturity of marketable securities, months | 13 months | 16 months

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- Definition Average remaining time to maturity of marketable debt securities, available-for-sale securities. + References No definition available. + Details
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- Definition Overnight reverse repurchase agreements, percent of total assets + References No definition available. + Details
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- References No definition available. + Details
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