Quarterly report pursuant to Section 13 or 15(d)

Investment Securities - Additional Information (Detail)

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Investment Securities - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Dec. 31, 2013
Investment Securities [Line Items]      
Other-than-temporary impairment charge $ 0    
Impairment charges on securities in continuous unrealized loss position for 12 months or longer 0   0
Net realized gain (loss) on redemption or sale of investment securities 1,421,000 9,000  
Recognized in earnings resulting from the redemption of investment securities 59,000 34,000  
Investment securities available-for-sale, carrying values 520,990,000   530,926,000
Securities Pledged as Collateral [Member]
     
Investment Securities [Line Items]      
Investment securities available-for-sale, carrying values $ 36,900,000   $ 47,600,000