Quarterly report pursuant to Section 13 or 15(d)

Securities - Additional Information (Detail)

v3.2.0.727
Securities - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
Investment Securities [Line Items]          
Other-than-temporary impairment charge     $ 0 $ 0 $ 0
Impairment charges on securities in continuous unrealized loss position for 12 months or longer $ 0   0   0
Net realized gains on sales of securities 1,912,000 $ 364,000 4,096,000 1,785,000  
Recognized in earnings resulting from the sale of securities 4,100,000 $ 100,000 1,200,000 $ 177,000  
Securities available for sale 728,683,000   728,683,000   1,060,717,000
Collateralized mortgage obligations [Member]          
Investment Securities [Line Items]          
Securities available for sale 155,369,000   155,369,000   188,047,000
Mortgage-backed securities [Member]          
Investment Securities [Line Items]          
Securities available for sale 379,568,000   $ 379,568,000   573,286,000
Mortgage-backed securities [Member] | Collateralized mortgage obligations [Member]          
Investment Securities [Line Items]          
Contractual maturities     2064    
Securities Pledged as Collateral [Member]          
Investment Securities [Line Items]          
Securities available for sale $ 71,100,000   $ 71,100,000   $ 76,200,000