Stock options, warrants and restricted common stock (Schedule of Stock-based Compensation) (Details) - USD ($) |
12 Months Ended | |
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Dec. 31, 2018 |
Dec. 31, 2017 |
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| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||
| Total stock-based compensation | $ 4,660,406 | $ 2,589,812 |
| Restricted stock awards under Plan [Member] | ||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||
| Total stock-based compensation | 3,971,916 | 1,714,116 |
| Stock option awards under Plan [Member] | ||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | ||
| Total stock-based compensation | $ 688,490 | $ 875,696 |
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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