Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Additional Information (Details)

v3.20.4
Stock-Based Compensation - Additional Information (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2018
shares
Dec. 31, 2020
USD ($)
item
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
shares
Additional Employee Stock Plans Information        
Income tax expense (benefit)   $ (12,276) $ 13,451 $ 11,854
Performance Share Unit Awards        
Additional Employee Stock Plans Information        
Compensation expenses recognized   567 1,420 $ 1,880
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest   535    
Performance Share Unit Awards | 2010 Plan        
Additional Employee Stock Plans Information        
Compensation expenses recognized   $ 2,263 $ 1,819  
Performance period   3 years    
Number of performance shares company expects participants to earn | shares   23,336 30,985 54,840
Number of performance shares units that will be converted into RSUs | shares 64,040      
Restricted stock units        
Additional Employee Stock Plans Information        
Vesting period of awards   2 years    
fair value per share of the awards | $ / shares   $ 49.90 $ 36.48  
Accelerated stock based compensation expense   $ 1,191 $ 1,374 $ 2,968
Restricted stock units | 2010 Plan        
Additional Employee Stock Plans Information        
Compensation expenses recognized       2,670
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest   $ 899    
Minimum age of employee, attaining which awards are continued to be vested upon retirement | item   65    
Minimum service period, upon serving which awards are continued to be vested upon retirement   10 years    
Minimum age of employee along with service period condition, attaining which awards are continued to be vested upon retirement | item   55    
Maximum period following a termination of service in which the share-based award will be settled   2 months 15 days    
Restricted stock units | 2010 Plan | Management        
Additional Employee Stock Plans Information        
Accelerated stock based compensation expense       $ 1,191
Restricted stock units | 2010 Plan | Common Stock        
Additional Employee Stock Plans Information        
Number of shares issued upon exercise of units other than options | shares   1