Stock-based compensation - Summary of Status of Company's Stock Option Activity (Details) - USD ($) |
6 Months Ended |
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Jun. 30, 2017 | |
| Number of Shares | |
| Beginning balance (in shares) | 1,857,012 |
| Granted (in shares) | 960,000 |
| Cancelled, expired, or forfeited (in shares) | 656,477 |
| Ending balance (in shares) | 2,160,535 |
| Exercisable at end of period (in shares) | 897,718 |
| Weighted Average Exercise Price | |
| Beginning balance (in dollars per share) | $ 4.28 |
| Granted (in dollars per share) | 2.13 |
| Cancelled, expired, or forfeited (in dollars per share) | 3.21 |
| Ending balance (in dollars per share) | 3.65 |
| Exercisable at end of period (in dollars per share) | $ 4.74 |
| Weighted Average Remaining Contractual Life (Years) | |
| Outstanding ending balance | 7 years 5 months 19 days |
| Exercisable at end of period | 5 years 1 month 24 days |
| Intrinsic Value | |
| Outstanding ending balance | $ 35,400 |
| Exercisable at end of period | $ 0.00 |
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- Definition Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Aggregate Intrinsic Value [Abstract]. No definition available.
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- References No definition available.
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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Gross number of share options (or share units) granted during the period. No definition available.
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Number of options outstanding, including both vested and non-vested options. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- References No definition available.
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- Definition Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated. No definition available.
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- Definition Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options. No definition available.
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- Definition Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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