Business Combinations - Schedule of Supplemental Pro Forma Information (Detail) (CBI [Member], USD $)
In Thousands, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
CBI [Member]
   
Business Acquisition [Line Items]    
Net interest income - pro forma (unaudited) $ 42,281 $ 36,073
Net earnings - pro forma (unaudited) $ 7,166 $ 5,401
Diluted earnings per common share (unaudited) $ 0.96 $ 0.73