Fair Value of Warrants - Assumptions Used in Computing Fair Value of Derivative Warrants (Details) - $ / shares |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2017 |
Mar. 31, 2018 |
Dec. 31, 2017 |
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| 2017 Debt | |||
| Class of Warrant or Right [Line Items] | |||
| Exercise price (in dollars per share) | $ 2.82 | $ 2.82 | $ 2.82 |
| Expected life (years) | 7 years | 5 years 11 months 23 days | 6 years 2 months 19 days |
| Expected volatility | 74.61% | 73.43% | 74.18% |
| Risk-free interest rate | 2.22% | 2.56% | 2.33% |
| Expected dividend yield | 0.00% | 0.00% | 0.00% |
| 2016 Offerings | |||
| Class of Warrant or Right [Line Items] | |||
| Exercise price (in dollars per share) | $ 2.25 | $ 2.25 | $ 2.25 |
| Expected life (years) | 4 years 9 months 15 days | 3 years 9 months 29 days | 4 years 29 days |
| Expected volatility | 76.29% | 100.00% | 73.44% |
| Risk-free interest rate | 1.94% | 2.39% | 2.11% |
| Expected dividend yield | 0.00% | 0.00% | 0.00% |
| 2017 Offering | |||
| Class of Warrant or Right [Line Items] | |||
| Exercise price (in dollars per share) | $ 2.36 | $ 2.36 | |
| Expected life (years) | 1 year 2 months 9 days | 1 year 5 months 5 days | |
| Expected volatility | 76.78% | 77.55% | |
| Risk-free interest rate | 2.09% | 1.83% | |
| Expected dividend yield | 0.00% | 0.00% |
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- Definition Fair Value Assumption, Exercise Price No definition available.
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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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- Definition Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Period the instrument, asset or liability is expected to be 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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- Definition Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Risk-free interest rate assumption used in valuing an instrument. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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