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Earnings per Common Share - Computation of Basic and Diluted Earnings per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator [Abstract]
Net income	$ 2,687	$ 1,543
Denominator [Abstract]
Weighted average shares outstanding – basic (in shares)	4,949,112	4,935,421
Potentially dilutive common shares – restricted stock units (in shares)	3,261	2,204
Weighted average shares outstanding – diluted (in shares)	4,952,373	4,937,625
Basic (in usd per share)	$ 0.54	$ 0.31
Diluted (in usd per share)	$ 0.54	$ 0.31

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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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Number of shares of restricted stock determined by relating the portion of time within a reporting period that restricted shares have been outstanding to the total time in that period. Restricted shares are subject to sales, contractual, regulatory or other restrictions that prevent or inhibit the holder from freely disposing of them before the restriction ends.

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