Earnings Per Share - Summary of Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share Basic [Abstract]
Net income, as reported	$ 10,549	$ 8,851
Less allocated income to unvested shares		15
Net income available to common shareholders-basic	10,549	8,836
Basic weighted average common shares	18,531,926	18,281,353
Basic earnings per common share	$ 0.57	$ 0.48
Net income available to common shareholders-diluted	$ 10,549	$ 8,836
Weighted average common shares	18,531,926	18,281,353
Stock options and performance shares	327,756	408,489
Diluted weighted average common shares	18,859,682	18,689,842
Diluted earnings per common share	$ 0.56	$ 0.47