Share-Based Compensation - Summary of Stock Option Activity (Detail) - $ / shares	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of options, Beginning balance	63,285	67,082
Number of options, Granted	8,300	8,240
Number of options, Exercised	(1,119)	(6,709)
Number of options, Expired	(5,029)	(5,328)
Number of options, Ending balance	65,437	63,285
Weighted Average Exercise price, Beginning balance	$ 15.12	$ 14.26
Weighted Average Exercise price granted	18.06	19.55
Weighted Average Exercise price, Exercised	14.11	12.72
Weighted Average Exercise price, Expired	14.43	14.37
Weighted Average Exercise price, Ending balance	15.55	15.12
Weighted Average Fair Value, Granted	$ 10.20	$ 13.80

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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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 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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