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Stock Based Compensation - Additional Information (Details)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
shares
Dec. 31, 2019
USD ($)
item
$ / shares
shares
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
$ / shares
Additional Employee Stock Plans Information          
Income tax expense (benefit)     $ 13,451 $ 11,854 $ (2,409)
Performance Share Unit Awards          
Additional Employee Stock Plans Information          
Compensation expenses recognized     1,420 1,880 $ 1,768
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest     781    
Performance Share Unit Awards | 2010 Plan          
Additional Employee Stock Plans Information          
Compensation expenses recognized     $ 1,819 $ 2,670  
Performance period     3 years    
Number of performance shares company expects participants to earn | shares     47,958 64,489  
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     $ 36.48   $ 33.60
Accelerated stock based compensation expense     $ 1,374 $ 2,968 $ 619
Restricted stock units | 2010 Plan          
Additional Employee Stock Plans Information          
Compensation expenses recognized         $ 1,732
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest     $ 733    
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    
Percentage of RSUs issued that will immediately vest and be converted into common shares 33.33%        
Percentage of RSUs issued that will vest ratably over the remaining vesting period 66.67%        
Restricted stock units | 2010 Plan | Management          
Additional Employee Stock Plans Information          
Accelerated stock based compensation expense       $ 1,374  
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