Share-based Compensation - Summary of Company's Stock Option Plan Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Shares, Options outstanding, Beginning balance	1,166
Number of Shares, Granted	116
Number of Shares, Exercised	(289)
Number of Shares, Forfeited	(35)
Number of Shares, Expired	0
Number of Shares, Options outstanding, Ending balance	958
Number of Shares, Options exercisable	771
Number of Shares, Available for grant	1,275
Weighted Average Exercise Price Per Share, Options outstanding, Beginning balance \| $ / shares	$ 14.66
Weighted Average Exercise Price Per Share, Granted \| $ / shares	19.99
Weighted Average Exercise Price Per Share, Exercised \| $ / shares	7.35
Weighted Average Exercise Price Per Share, Forfeited \| $ / shares	18.30
Weighted Average Exercise Price Per Share, Expired \| $ / shares	0
Weighted Average Exercise Price Per Share, Options outstanding, Ending balance \| $ / shares	17.39
Weighted Average Exercise Price Per Share, Options exercisable \| $ / shares	$ 16.99
Weighted Average Remaining Contractual Life (Years), Options outstanding	7 years 1 month 6 days
Weighted Average Remaining Contractual Life (Years), Options exercisable	6 years 9 months 18 days
Aggregate Intrinsic Value, Options outstanding \| $	$ 8,747
Aggregate Intrinsic Value, Options exercisable \| $	$ 7,351

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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

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