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Stock Incentive Plan (Tables) | 6 Months Ended
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Jun. 30, 2019
Stock Incentive Plan |
Schedule of weighted-average assumptions for options granted | ​
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Six months ended June 30, |  | 2019 | ​ | 2018 |
​ | ​ | ​
Expected term (in years) |  | 5.76 | ​ | 6.22 | ​
Expected volatility |  | 53.90 | % | 49.74 | %
Risk free rate |  | 1.87 | % | 2.55 | %
Expected dividends |  | — | % | — | %

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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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