Stockholders' Equity - Summary of the Company's Stock Options Activity (Detail) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Number of Option, Granted (in shares)	0	0	0
Number of Options expected to vest, end of year (in shares)	1,100,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding
Number of Options outstanding, beginning of year (in shares)	804,000	1,008,000	1,103,000
Number of Option, Granted (in shares)	6,366,000.000	0	0
Number of Options, Exercised (in shares)	(664,000)	(198,000)	(95,000)
Number of Options, Expired / terminated (in shares)	(48,000)	(6,000)	0
Number of Options outstanding, end of year (in shares)	6,458,000	804,000	1,008,000
Number of Options exercisable, end of year (in shares)	92,000	775,000	977,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Options outstanding, beginning of year (in dollars per share)	$ 4.99	$ 5.40	$ 5.37
Weighted Average Exercise Price, Granted (in dollars per share)	28.58	0.00	0.00
Weighted Average Exercise Price, Exercised (in dollars per share)	5.09	6.99	5.02
Weighted Average Exercise Price, Expired / terminated (in dollars per share)	4.55	8.32	0.00
Weighted Average Exercise Price, Options outstanding, end of year (in dollars per share)	28.24	4.99	5.40
Weighted Average Exercise Price, Options exercisable, end of year (in dollars per share)	$ 4.45	$ 5.00	$ 5.42

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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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

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