Earnings Per Share - Computation for Earnings Per Share (Detail) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net Income	$ 9,512,622us-gaap_NetIncomeLoss	$ 5,749,598us-gaap_NetIncomeLoss
Weighted average shares outstanding
Basic (in shares)	3,218,154	3,165,940
Dilutive impact of restricted stock grants with forfeitable rights to dividends	74,076	63,326
Dilutive impact of restricted stock units	3,938	1,634
Diluted (in shares)	3,296,168	3,230,900
Earnings per share
Basic (USD per share)	$ 2.96us-gaap_EarningsPerShareBasic	$ 1.82us-gaap_EarningsPerShareBasic
Diluted (USD per share)	$ 2.89us-gaap_EarningsPerShareDiluted	$ 1.78us-gaap_EarningsPerShareDiluted

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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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Nonvested equity-based payment awards that contain forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) that result in incremental common shares.

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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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