| Short-term investments |
4. Short‑term investments
Short‑term investments by investment type consisted of the following:
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December 31, 2019
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Gross unrealized
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Gross unrealized
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Amortized cost
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gains
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losses
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Fair value
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Commercial paper
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$
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42,148
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$
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24
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$
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—
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$
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42,172
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US Government agency bonds
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13,045
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—
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(9)
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13,036
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US Treasury bonds
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28,107
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—
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(2)
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28,105
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Corporate debt securities
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34,562
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5
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(3)
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34,564
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$
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117,862
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$
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29
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$
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(14)
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$
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117,877
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March 31, 2019
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Gross unrealized
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Gross unrealized
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Amortized cost
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gains
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losses
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Fair value
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Commercial paper
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$
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46,687
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$
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2
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$
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(2)
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$
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46,687
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US Government agency bonds
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15,889
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4
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—
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15,893
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US Treasury bonds
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38,047
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13
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—
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38,060
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Corporate debt securities
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8,469
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—
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(2)
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8,467
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$
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109,092
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$
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19
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$
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(4)
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$
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109,107
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