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)

v3.2.0.727
Fair Value Measurements - Reconciliation and Income Statement Classification of Gains and Losses for All Assets and Liabilities (Detail)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2015
USD ($)
Security
Jun. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
Security
Jun. 30, 2014
USD ($)
Dec. 31, 2014
USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Estimated Fair Value $ 728,683   $ 728,683   $ 1,060,717
Gross realized losses on sales of securities $ (155) $ (1) $ (166) $ (1)  
Equity security [Member]          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Number of equity securities | Security 2   2    
Recurring Basis [Member]          
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]          
Estimated Fair Value $ 728,683   $ 728,683   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