Earnings Per Share - Reconciliation of Weighted Average Shares used for Basic and Diluted Earnings Per Share Calculation (Detail) - shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Basic weighted average common shares	19,248,657	19,208,978	19,165,489
Add: Other common shares eligible for common dividends:
Stock options and restricted stock	80,581	84,104	80,377
Diluted weighted average common shares	19,329,238	19,293,082	19,245,866

Weighted Average Number Of Shares Other [Abstract]

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- References

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
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- Definition

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.

+ References

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 260
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