Stock-Based Compensation - Summary of Stock Option Activity for Company's Stock Option Plans (Detail) shares in Thousands	12 Months Ended
Dec. 31, 2019 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, Beginning Balance, Number of Shares \| shares	4,160
Options granted, Number of Shares \| shares	1,716
Options forfeited or expired, Number of Shares \| shares	(720)
Outstanding, Ending Balance, Number of Shares \| shares	5,156
Vested and expected to vest as of December 31, 2019, Number of Shares \| shares	5,156
Exercisable as of December 31, 2019, Number of Shares \| shares	3,151
Outstanding, Beginning Balance, Weighted Average Exercise Price Per Share \| $ / shares	$ 3.66
Options granted, Weighted Average Exercise Price Per Share \| $ / shares	1.00
Options forfeited or expired, Weighted Average Exercise Price Per Share \| $ / shares	3.27
Outstanding, Ending Balance, Weighted Average Exercise Price Per Share \| $ / shares	2.73
Vested and expected to vest as of December 31, 2019, Weighted Average Exercise Price Per Share \| $ / shares	2.73
Exercisable as of December 31, 2019, Weighted Average Exercise Price Per Share \| $ / shares	$ 3.56
Outstanding, Weighted Average Remaining Contractual Term (Years)	8 years 2 months 8 days
Vested and expected to vest as of December 31, 2019, Weighted Average Remaining Contractual Term (Years)	8 years 2 months 8 days
Exercisable as of December 31, 2019, Weighted Average Remaining Contractual Term (Years)	7 years 8 months 23 days

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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 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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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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