XML 84 R70.htm IDEA: XBRL DOCUMENT v3.6.0.2
Investment Securities - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]      
Maturity of contract less than one year    
Approximate year of maturity 30 years    
Gross Unrealized Gains (Losses) $ 18,546 $ 16,477  
Securities available for sale 778,612 886,560  
Amortized Cost 790,082 891,111  
Gain (loss) on sales of securities 617 (153) $ 550
Available-for-sale securities pledged as collateral 445,800 416,100  
Held-to-maturity securities pledged as collateral 119,200 $ 45,700  
US Government Agencies Debt Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Sale of available securities 75,000    
Gain (loss) on sales of securities $ (300)