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Investment Securities - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2014
Security
Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]    
Number of debt securities continues loss position for more than twelve months 10us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear  
Number of debt securities continues loss position for less than twelve months 31us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear  
Investment securities available-for-sale carrying amount $ 61,100,000us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral $ 72,700,000us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
Gains realized on sales of securities available-for-sale 104,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet 484,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet
Losses on sales of securities $ 0us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses $ 0us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses