Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Numerator for basic and diluted earnings per share -income available to common shareholders:
Net income	$ 15,973	$ 17,774	$ 33,180	$ 29,372
Dividends on preferred stock	0	0	0	1,865
Income available to common shareholders	$ 15,973	$ 17,774	$ 33,180	$ 27,507
Denominator for basic earnings per share - weighted average shares	57,694,792	57,539,901	57,642,970	56,356,877
Effect of dilutive securities -
Employee stock awards	945,250	944,176	974,958	893,621
Warrants	94,620	119,962	104,520	114,824
Denominator for diluted earnings per share - adjusted weighted average shares	58,734,662	58,604,039	58,722,448	57,365,322
Earnings per share available to common shareholders
Basic	$ 0.28	$ 0.31	$ 0.58	$ 0.49
Diluted	$ 0.27	$ 0.30	$ 0.57	$ 0.48

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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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