Share-Based Compensation - Summary of Stock Award Activity for the Period (Detail)	6 Months Ended
Jun. 30, 2019 $ / shares shares
Share Based Arrangements To Obtain Goods And Services [Abstract]
Number of Shares, Awards outstanding, Beginning balance \| shares	1,767,503
Number of Shares, Granted \| shares	995,500
Number of Shares, Forfeited \| shares	(186,292)
Number of Shares, Awards outstanding, Ending balance \| shares	2,576,711
Number of Shares, Options exercisable \| shares	1,338,567
Number of Shares, Options exercisable, Weighted average remaining contractual term	6 years 9 months 18 days
Number of Shares, Options vested and expected to vest \| shares	2,524,818
Number of Shares, Options vested and expected to vest, Weighted average remaining contractual term	8 years
Weighted-Average Exercise Price, Awards outstanding, Beginning balance \| $ / shares	$ 8.57
Weighted-Average Exercise Price, Granted \| $ / shares	2.26
Weighted-Average Exercise Price, Forfeited \| $ / shares	5.99
Weighted-Average Exercise Price, Awards outstanding, Ending balance \| $ / shares	6.32
Weighted-Average Exercise Price, Options exercisable \| $ / shares	9.45
Weighted-Average Exercise Price, Options vested and expected to vest \| $ / shares	$ 6.39

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
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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.

+ References

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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.

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-Publisher FASB
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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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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.

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Weighted average remaining contractual term for fully vested and expected to vest exercisable or convertible options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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