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Investment Securities - Additional Information (Detail)
12 Months Ended
Dec. 31, 2015
USD ($)
Securities
Dec. 31, 2014
USD ($)
Securities
Dec. 31, 2013
USD ($)
Schedule of Available-for-sale Securities [Line Items]      
Number of securities in an unrealized loss position | Securities 107 97  
Percentage of combined depreciation of the combined reported value of the aggregate securities portfolio 2.44% 3.21%  
Carrying amount of available-for-sale securities pledged $ 236,730,000 $ 268,780,000  
OTTI charges incurred   737,000 $ 320,000
Continuous Loss Position More Than Twelve Months      
Schedule of Available-for-sale Securities [Line Items]      
Number of securities in an unrealized loss position | Securities 48    
Debt Securities      
Schedule of Available-for-sale Securities [Line Items]      
OTTI charges incurred $ 0 0  
Non Agency Mortgage Backed Securities      
Schedule of Available-for-sale Securities [Line Items]      
OTTI charges incurred 0 705,000 320,000
Equity Securities      
Schedule of Available-for-sale Securities [Line Items]      
OTTI charges incurred $ 0 $ 32,000 $ 0