v3.3.1.900
Stock-based Compensation - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Stock Based Compensation [Line Items]      
Compensation expense related to incentive plans $ 5,800,000 $ 4,800,000 $ 2,400,000
Non-Voting Time-Vested Restricted Stock Units [Member]      
Stock Based Compensation [Line Items]      
Weighted average grant date fair value $ 30.17 $ 43.25  
Aggregate value of vested shares $ 900,000 $ 300,000  
Recognized / Unrecognized compensation cost $ 3,400,000    
Weighted average period 1 year 6 months 22 days    
Aggregate value of forfeited shares $ 200,000 $ 0  
Non-Voting Performance Based Restricted Stock Units [Member]      
Stock Based Compensation [Line Items]      
Weighted average grant date fair value $ 33.41    
Aggregate value of vested shares $ 3,300,000    
Recognized / Unrecognized compensation cost $ 7,400,000    
Weighted average period 1 year 9 months 29 days    
Aggregate value of forfeited shares $ 200,000    
2012 Long - Term Incentive Plan [Member] | Amended and Restated 2015 Long Term Incentive Plan [Member]      
Stock Based Compensation [Line Items]      
Shares available for issuance 721,572    
Forfeiture restrictions percentage 100.00%    
Vesting period of employees 3 years    
2012 Long - Term Incentive Plan [Member] | Amended and Restated 2015 Long Term Incentive Plan [Member] | Non-Voting Common Stock [Member]      
Stock Based Compensation [Line Items]      
Common stock authorized to issue 1,500,000