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Stock Compensation Plans - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2011
Dec. 31, 2010
Jun. 01, 2006
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]            
Restricted stock-based compensation expense $ 7,197,000 $ 6,457,000 $ 4,732,000      
Cash received from options exercised 0 $ 0 $ 0      
Restricted stock, unrecognized stock-based compensation cost $ 15,900,000          
Restricted stock, weighted-average remaining requisite service period 2 years 6 months          
25% of the shares issued            
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]            
Incentive restricted stock issued 135,440 293,904 187,056 182,728 418,716  
Shares granted exercise price $ 0 $ 0 $ 0 $ 0 $ 0  
Percentage of shares vested 25.00% 25.00% 25.00% 25.00% 25.00%  
Employee Stock Option            
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]            
Common stock reserved for issuance           16,000,000
Options granted vesting period 4 years          
Employee Stock Option | Maximum            
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]            
Options granted vesting period 10 years