Earnings Per Share - Computation of Basic and Diluted Earning Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Common Share [Line Items]
Net income allocable to common stockholders	$ 9,286	$ 6,094	$ 21,676	$ 14,438
Denominator for basic earnings per share - weighted average shares	8,712	8,605	8,702	8,594
Effect of dilutive employee stock options and warrants	83	96	77	124
Denominator for diluted earnings per share - adjusted weighted average shares and assumed exercise	8,795	8,701	8,779	8,718
Net income allocable to common shareholders	$ 1.07	$ 0.71	$ 2.49	$ 1.68
Net income allocable to common shareholders	$ 1.06	$ 0.70	$ 2.47	$ 1.66
Outstanding common stock equivalents having no dilutive effect	338	537	361	538

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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+ Details

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

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.

+ References+ Details

- 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+ Details

- Definition

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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+ Details