Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Basic
Net income	$ 4,725	$ 3,171
Preferred stock dividends	391	404
Net income available to common shareholders - basic	$ 4,334	$ 2,767
Weighted average common shares outstanding - basic	7,860,716	7,758,998
Basic earnings per common share	$ 0.55	$ 0.36
Diluted
Net income available to common shareholders - basic	$ 4,334	$ 2,767
Preferred stock dividends	391	404
Net income available to common shareholders - diluted	$ 4,725	$ 3,171
Weighted average common shares outstanding for basic earnings per common share basic	7,860,716	7,758,998
Add: Dilutive effects of convertible preferred shares	3,078,245	3,148,676
Average shares and dilutive potential common shares outstanding - diluted	10,938,961	10,907,674
Diluted earnings per common share	$ 0.43	$ 0.29