Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Reconciliation and Income Statement Classification of Gains and Losses for All Assets and Liabilities (Detail)

v3.3.1.900
Fair Value Measurements - Reconciliation and Income Statement Classification of Gains and Losses for All Assets and Liabilities (Detail)
$ in Thousands
 3 Months Ended 12 Months Ended
Jun. 30, 2015
USD ($)
Security
Dec. 31, 2015
USD ($)
Security
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Estimated Fair Value   $ 698,296 $ 1,060,717  
Gross realized losses on sales of investment securities   $ 165 1 $ 563
Equity securities [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Number of equity securities | Security 1 2    
Equity securities [Member] | Security One [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Book value     200  
Estimated Fair Value     200  
Equity securities [Member] | Security Two [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Book value     250  
Estimated Fair Value     214  
Gross realized losses on sales of investment securities $ 75      
Recurring Basis [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Estimated Fair Value   $ 698,296 1,060,717  
Significant Unobservable Inputs [Member] | Recurring Basis [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Estimated Fair Value   0 1,123  
Significant Unobservable Inputs [Member] | Recurring Basis [Member] | Municipal bonds-tax exempt [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance   709    
Purchases, Issuances and Settlement   (709)    
Realized Gains or (Losses) in Earnings   0    
Unrealized Gains or (Losses) in Other Comprehensive Income   0    
Ending Balance   0 709  
Significant Unobservable Inputs [Member] | Recurring Basis [Member] | Equity securities [Member]        
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]        
Beginning Balance   414    
Purchases, Issuances and Settlement   (339)    
Realized Gains or (Losses) in Earnings   (75)    
Unrealized Gains or (Losses) in Other Comprehensive Income   0    
Ending Balance   $ 0 $ 414