Earnings per Share - Schedule of Computation of Basic and Diluted EPS (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Net Income	$ 14,185	$ 5,450
Noncontrolling interests	(225)
Allocation of earnings to preferred stockholders		(64)
Net income attributable to common stockholders	$ 13,960	$ 5,386
Shares (in thousands):
Basic: Weighted-average number of shares outstanding	7,820	7,468
Plus: Incremental shares from assumed conversion of dilutive instruments	268	498
Diluted: Weighted-average number of shares outstanding	8,088	7,966
Earnings per share - Basic	$ 1.79	$ 0.72
Earnings per share - Diluted	$ 1.73	$ 0.68

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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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Amount of Net Income (Loss) attributable to redeemable noncontrolling interest.

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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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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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