Investment Securities - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]      
Proceeds from sale of securities available-for-sale $ 35,377,000 $ 952,000 $ 0
Realized gross gain (loss) from sale of investment (33,000) 47,000  
Mortgage-Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total number of securities 13 14  
Number of securities in loss position 3 3  
Municipal Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total number of securities 9 9  
Number of securities in loss position 1 4  
Mutual Fund [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Number of securities in loss position   1  
Securities Pledged [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Securities carrying value $ 34,633,000 $ 35,206,000