Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Basic earnings per common share computation:
Net income per consolidated statements of income	$ 6,480	$ 5,019
Net earnings allocated to participating securities	(39)	(31)
Net earnings allocated to common stock	$ 6,441	$ 4,988
Weighted average common shares outstanding, including shares considered participating securities	14,979	14,436
Less: Average participating securities	(86)	(79)
Weighted average shares	14,893	14,357
Basic earnings per common share	$ 0.43	$ 0.35
Diluted earnings per common share computation:
Net earnings allocated to common stock	$ 6,441	$ 4,988
Weighted average common shares outstanding for basic earnings per common share	14,893	14,357
Add: Dilutive effects of assumed exercises of stock options	0	0
Weighted average shares and dilutive potential common shares	14,893	14,357
Diluted earnings per common share	$ 0.43	$ 0.35
Distributed Earnings Allocated to Common Stock [Member]
Basic earnings per common share computation:
Net earnings allocated to common stock	$ 2,508	$ 2,369
Undistributed Earnings Allocated to Common Stock [Member]
Basic earnings per common share computation:
Net earnings allocated to common stock	$ 3,933	$ 2,619

Average participating securities.

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- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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Amount of earnings (loss) distributed and earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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The weighted average number of shares (units) outstanding in the calculation of pro forma basic earnings per share (earnings per unit), which is commonly presented in initial public offerings based on the terms of the offering.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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