Stock-Based Compensation - Summary of Stock Option Activity (Detail) - $ / shares	9 Months Ended
Sep. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options, Outstanding beginning balance	972,569
Number of options, Granted	651,600
Number of options, Forfeited or expired	(535,493)
Number of options, Outstanding ending balance	1,088,676
Number of options, Exercisable	355,845
Number of options, Vested and expected to vest	1,082,710
Weighted average exercise price, Outstanding beginning balance	$ 23.85
Weighted average exercise price, Granted	1.06
Weighted average exercise price, Forfeited or expired	23.77
Weighted average exercise price, Outstanding ending balance	10.25
Weighted average exercise price, Exercisable	26.24
Weighted average exercise price, Vested and expected to vest	$ 10.28
Weighted average remaining contractual term, Outstanding ending balance	8 years 10 months 9 days
Weighted average remaining contractual term, Exercisable	7 years 9 months 7 days
Weighted average remaining contractual term, Vested and expected to vest	8 years 10 months 9 days

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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.

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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.

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For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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

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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 options outstanding that can 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 options outstanding. 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 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 option awards outstanding, 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 options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents 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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