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Fair Value of Investments (Tables) | 6 Months Ended
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Jun. 30, 2019
Fair Value of Investments |
Summary of fair value financial assets measured on a recurring basis | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | (Level 1) | ​ | (Level 2) | ​ | (Level 3) | ​ | Total
June 30, 2019 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Assets: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Money market funds | ​ | $ | 13,421 | ​ | $ | — | ​ | $ | — | ​ | $ | 13,421
U.S. government securities | ​ | ​ | 14,943 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 14,943
Corporate bonds | ​ | ​ | — | ​ | ​ | 16,089 | ​ | ​ | — | ​ | ​ | 16,089
Commercial paper | ​ | ​ | — | ​ | ​ | 31,977 | ​ | ​ | — | ​ | ​ | 31,977
Asset-backed securities | ​ | ​ | — | ​ | ​ | 15,176 | ​ | ​ | — | ​ | ​ | 15,176
Total assets | ​ | $ | 28,364 | ​ | $ | 63,242 | ​ | $ | — | ​ | $ | 91,606
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | (Level 1) | ​ | (Level 2) | ​ | (Level 3) | ​ | Total
December 31, 2018 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Assets: | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Money market funds | ​ | $ | 12,947 | ​ | $ | — | ​ | $ | — | ​ | $ | 12,947
U.S. government securities | ​ | ​ | 15,923 | ​ | ​ | — | ​ | ​ | — | ​ | ​ | 15,923
Corporate bonds | ​ | ​ | — | ​ | ​ | 31,495 | ​ | ​ | — | ​ | ​ | 31,495
Commercial paper | ​ | ​ | — | ​ | ​ | 27,869 | ​ | ​ | — | ​ | ​ | 27,869
Asset-backed securities | ​ | ​ | — | ​ | ​ | 17,025 | ​ | ​ | — | ​ | ​ | 17,025
Total assets | ​ | $ | 28,870 | ​ | $ | 76,389 | ​ | $ | — | ​ | $ | 105,259

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- Definition Tabular disclosure of assets, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, by class that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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