Earnings Per Share - Reconciles Numerators and Denominators of Basic Earnings Per Share with Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator for Earnings per Share-Basic:
Net income	$ 14,033	$ 12,330
Less: Income allocated to participating shares	35	45
Net Income Allocated to Shareholders	13,998	12,285
Numerator for Earnings per Share-Diluted:
Net income	14,033	12,330
Net Income Available to Shareholders	$ 14,033	$ 12,330
Denominators:
Weighted Average Shares Outstanding-Basic	29,660,794	29,621,453
Add: Dilutive potential shares	37,253	52,953
Denominator for Treasury Stock Method-Diluted	29,698,047	29,674,406
Weighted Average Shares Outstanding-Basic	29,660,794	29,621,453
Add: Average participating shares outstanding	74,237	108,249
Denominator for Two-Class Method-Diluted	29,735,031	29,729,702
Earnings per share—basic (in dollars per share)	$ 0.47	$ 0.41
Earnings per share—diluted (in dollars per share)	$ 0.47	$ 0.41
Warrants [Member]
Denominators:
Anti-dilutive excluded from dilutive potential shares	517,012	517,012
Stock Options [Member]
Denominators:
Anti-dilutive excluded from dilutive potential shares	428,863	655,573
Restricted Stock [Member]
Denominators:
Anti-dilutive excluded from dilutive potential shares	36,984	55,296