Fair Value Measurements - Summary of Warrants Liability and Remeasured Liability to Estimated Fair Value (Detail)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Risk-free interest rate	2.09%	1.93%
Expected volatility	100.39%	94.19%
Expected term	4 years 29 days	5 years 29 days
Expected dividend yield	0.00%	0.00%

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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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.

+ References

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- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

+ References

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- Definition

Risk-free interest rate assumption used in valuing an instrument.

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- References

No definition available.

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