Quarterly report pursuant to Section 13 or 15(d)

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

v3.3.0.814
Fair Value Measurements - Reconciliation and Income Statement Classification of Gains and Losses for All Assets and Liabilities (Detail)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2015
USD ($)
Security
Jun. 30, 2015
USD ($)
Security
Sep. 30, 2014
USD ($)
Sep. 30, 2015
USD ($)
Security
Sep. 30, 2014
USD ($)
Dec. 31, 2014
USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]            
Estimated Fair Value $ 669,340     $ 669,340   $ 1,060,717
Gross realized losses on sales of securities $ 0   $ 0 $ (166) $ (1)  
Equity security [Member]            
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]            
Number of equity securities | Security 2 1   2    
Recurring Basis [Member]            
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]            
Estimated Fair Value $ 669,340     $ 669,340   1,060,717
Security One [Member] | Equity security [Member]            
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]            
Book value of equity security           200
Estimated Fair Value           200
Security Two [Member] | Equity security [Member]            
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]            
Book value of equity security           250
Estimated Fair Value           214
Gross realized losses on sales of securities   $ (75)        
Fair Value, Inputs, Level 3 [Member] | Recurring Basis [Member]            
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]            
Estimated Fair Value 0     0   $ 1,123
Fair Value, Inputs, Level 3 [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     0    
Fair Value, Inputs, Level 3 [Member] | Recurring Basis [Member] | Equity security [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     $ 0