Calculation for Basic and Diluted Earnings per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Calculation For Basic And Diluted Earnings Per Common Share [Line Items]
Net income	$ 7,007	$ 5,435	$ 12,732	$ 12,576
Dividends on preferred stock	227	253	455	511
Net income available to common shareholders	$ 6,780	$ 5,182	$ 12,277	$ 12,065
Weighted average number of common shares outstanding, basic	18,395,996	19,997,991	18,409,414	20,015,247
Convertible preferred stock	1,045,419	1,183,851	1,046,944	1,192,900
Weighted average number of common shares outstanding, diluted	19,457,237	21,205,078	19,475,333	21,231,615
Basic earnings per common share	$ 0.37	$ 0.26	$ 0.67	$ 0.60
Diluted earnings per common share	$ 0.36	$ 0.26	$ 0.65	$ 0.59
Stock Option
Calculation For Basic And Diluted Earnings Per Common Share [Line Items]
Stock attributable to share based compensation	15,577	15,952	18,467	16,512
Total potential antidilutive shares	253,082	337,693	253,082	337,693
Restricted Stock
Calculation For Basic And Diluted Earnings Per Common Share [Line Items]
Stock attributable to share based compensation	245	7,284	508	6,956

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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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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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