Stock-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning balance, options	335,000
Granted, options	46,500
Exercised, options	(105,860)
Forfeited, options	(9,330)
Ending balance, options	266,310
Exercisable options, ending balance	8,830
Beginning balance, weighted average exercise price \| $ / shares	$ 34.75
Ending balance, weighted average exercise price \| $ / shares	38.93
Exercisable, weighted average exercisable price \| $ / shares	$ 43.01
Outstanding, weighted average remaining contractual life (years)	4 years 7 months 6 days
Exercisable, weighted average remaining contractual life (years)	3 years 1 month 6 days
Outstanding, aggregate intrinsic value \| $	$ 5,289
Exercisable, aggregate intrinsic value \| $	$ 113

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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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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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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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