Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Earnings per share basic and diluted [Abstract]
Net income applicable to common stock	$ 4,247	$ 3,303
Basic earnings per share computation [Abstract]
Weighted average common shares outstanding (in shares)	3,478,280	3,479,180
Earnings per share - basic (in dollars per share)	$ 1.22	$ 0.94
Diluted earnings per share computation [Abstract]
Weighted average common shares outstanding for basic earnings per share (in shares)	3,478,280	3,479,180
Add: Dilutive effects of restricted stock (in shares)	363	20
Weighted average common shares outstanding for dilutive earnings per share (in shares)	3,478,643	3,479,200
Earnings per share - diluted (in dollars per share)	$ 1.22	$ 0.94
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive restricted stock excluded from net income per share calculations (in shares)	426	2,087
Restricted Stock [Member] \| Minimum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive stock share price range (in dollars per share)	$ 49.87	$ 49.87
Restricted Stock [Member] \| Maximum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive stock share price range (in dollars per share)	$ 61.04	$ 53.15

Agreed-upon price for the exchange of the underlying asset relating to the share-based payment award.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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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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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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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.

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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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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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