Share-Based Compensation - Summary of Stock Option Activity (Detail)	6 Months Ended
Jun. 30, 2019 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning balance of Outstanding, Options \| shares	2,818,000
Exercised, Options \| shares	(4,000)
Cancelled, Options \| shares	(164,000)
Ending balance of Outstanding, Options \| shares	2,650,000
Exercisable, Options \| shares	2,073,000
Beginning balance of Outstanding, Weighted Average Exercise Price \| $ / shares	$ 9.59
Exercised, Weighted Average Exercise Price \| $ / shares	7.33
Cancelled, Weighted Average Exercise Price \| $ / shares	22.62
Ending balance of Outstanding, Weighted Average Exercise Price \| $ / shares	8.79
Exercisable, Weighted Average Exercise Price \| $ / shares	$ 8.85

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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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Number of share options (or share units) exercised during the current period.

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