Annual report pursuant to Section 13 and 15(d)

Securities - Additional Information (Detail)

v3.3.1.900
Securities - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]      
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 6,611,000 2,011,000 $ 1,039,000
Recognized in earnings resulting from the redemption of investment securities 1,900,000 (498,000) $ 3,300,000
Investment securities available-for-sale, market values 698,296,000 1,060,717,000  
Securities Pledged as Collateral [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Investment securities available-for-sale, market values $ 72,000,000 $ 76,200,000