Earnings Per Share - Computation of Basic and Diluted Earnings (Loss) Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net Income, Basic	$ 10,799	$ 2,232	$ 16,841	$ 10,584
Net Income, Diluted	$ 10,799	$ 2,232	$ 16,841	$ 10,584
Weighted Average Number of Shares Outstanding, Basic	2,356,766	2,415,303	2,367,602	2,448,743
Weighted Average Number of Shares Outstanding, Options	754,847	749,664	753,464	743,966
Weighted Average Number of Shares Outstanding, Diluted	3,111,613	3,164,967	3,121,066	3,192,709
Net Income Per Share, Basic	$ 4.58	$ 0.92	$ 7.11	$ 4.32
Net Income Per Share, Diluted	$ 3.47	$ 0.71	$ 5.40	$ 3.32

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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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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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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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