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v3.20.4

Investments (Tables) | 12 Months Ended
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Dec. 31, 2020
Investments |
Schedule of amortized cost and fair value of available-for-sale securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | Gross |  | Gross |  | ​
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | Estimated
​ | ​ | Cost | ​ | Gains | ​ | Losses | ​ | Fair Value
​ | ​ | (in thousands)
December 31, 2020 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. treasuries | ​ | $ | 149,206 | ​ | $ | 14 | ​ | $ | (1) | ​ | $ | 149,219
Corporate debt | ​ | ​ | 32,588 | ​ | ​ | — | ​ | ​ | (34) | ​ | ​ | 32,554
Commercial paper | ​ | ​ | 7,997 | ​ | ​ | 1 | ​ | ​ | — | ​ | ​ | 7,998
Total | ​ | $ | 189,791 | ​ | $ | 15 | ​ | $ | (35) | ​ | $ | 189,771
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
December 31, 2019 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. treasuries | ​ | $ | 105,096 | ​ | $ | 38 | ​ | $ | (4) | ​ | $ | 105,130
Government agency securities | ​ | ​ | 1,139 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 1,139
Corporate debt | ​ |  | 6,003 | ​ |  | — | ​ |  | (1) | ​ |  | 6,002
Commercial paper | ​ | ​ | 2,981 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 2,981
Total | ​ | $ | 115,219 | ​ | $ | 38 | ​ | $ | (5) | ​ | $ | 115,252
Schedule of fair value and unrealized losses of available-for-sale securities in a loss position | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2020 | ​ | December 31, 2019
​ |  | ​ | ​ |  | Gross |  | ​ |  | Gross
​ | ​ | Estimated | ​ | Unrealized | ​ | Estimated | ​ | Unrealized
​ | ​ | Fair Value | ​ | Losses | ​ | Fair Value | ​ | Losses
​ | ​ | ​ | (in thousands)
U.S. treasuries | ​ | $ | 19,991 | ​ | $ | (1) | ​ | $ | 22,943 | ​ | $ | (4)
Corporate debt | ​ |  | 32,554 | ​ |  | (34) | ​ |  | 6,002 | ​ |  | (1)
Total | ​ | $ | 52,545 | ​ | $ | (35) | ​ | $ | 28,945 | ​ | $ | (5)

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