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Stock Compensation Plans - Additional Information (Detail)
3 Months Ended 12 Months Ended
Nov. 30, 2016
Jun. 08, 2016
shares
Sep. 30, 2016
$ / shares
Dec. 31, 2016
USD ($)
$ / shares
shares
Dec. 31, 2015
USD ($)
$ / shares
shares
Dec. 31, 2014
USD ($)
$ / shares
shares
Jun. 01, 2006
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Restricted stock-based compensation expense | $       $ 6,651,000 $ 7,197,000 $ 6,457,000  
Dividends per share declared | $ / shares     $ 15.00 $ 15.00 $ 0.00 $ 0.00  
Dividend payable, date to be paid     Oct. 03, 2016        
Dividend payable, record date     Sep. 22, 2016        
Additional compensation cost | $       $ 1,500,000      
Cash received from options exercised | $       0 $ 0 $ 0  
Restricted stock unit, unrecognized stock-based compensation cost | $       $ 15,900,000      
Restricted stock unit, weighted-average remaining requisite service period       3 years 1 month 6 days      
25% of the shares issued              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Incentive restricted stock unit issued       415,519 135,440 293,904  
Shares granted exercise price | $ / shares       $ 0 $ 0 $ 0  
Percentage of shares vested       25.00% 25.00% 25.00%  
Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of restricted stock units issuance as percentage of stock options granted 25.00%            
RSUs will be forfeited if Purchased Shares does not equal threshold of remaining RSUs from Grant 4            
Restricted Stock | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Purchase price that equal to up to percentage of the employee's base salary 25.00%            
Amended Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock option issued       0 0    
Amended Plan | Employee Stock Option              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Common stock reserved for issuance             16,000,000
Options granted vesting period       4 years      
Amended Plan | Employee Stock Option | Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Options granted vesting period       10 years      
2016 Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Stock option issued       0 0    
2016 Plan | Employee Stock Option              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Common stock reserved for issuance   16,000,000          
Options granted vesting period   4 years