Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Fair Value Assumptions Expected volatility Rate Maximum	85.00%	81.10%
Fair Value Assumptions Risk Free Interest Rate Maximum	2.53%	2.74%
Fair Value Assumptions Expected Term1		6 years
Fair Value Assumptions Expected Dividend Rate	0.00%	0.00%
Private Placement [Member]
Number of securities into which the class of warrant converted	18,939,394
Warrant Exercise Per share	$ 3.01
fair value of adjustment of warrants	$ 18.4
Fair Value Assumptions Expected volatility Rate Maximum	71.00%
Fair Value Assumptions Risk Free Interest Rate Maximum	2.99%
Fair Value Assumptions Expected Term1	5 years
Fair Value Assumptions Expected Dividend Rate	0.00%

Exercise price per share or per unit of warrants or rights outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
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- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

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- Definition

Amount of expense (income) related to adjustment to fair value of warrant liability.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the maximum percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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