Quarterly report pursuant to Section 13 or 15(d)

Employee Stock Plans - Additional Information (Details)

v3.19.1
Employee Stock Plans - Additional Information (Details)
$ in Thousands
 3 Months Ended
Mar. 31, 2019
USD ($)
item
shares
Mar. 31, 2018
USD ($)
Additional Employee Stock Plans Information    
Income tax benefit $ (463) $ (1,262)
Performance Share Unit Awards    
Additional Employee Stock Plans Information    
Compensation expenses recognized 294 491
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest $ 1,729  
Restricted stock units    
Additional Employee Stock Plans Information    
Vesting period of awards 2 years  
Restricted stock units | Non-employee director    
Additional Employee Stock Plans Information    
Number of shares issued upon exercise of units other than options | shares 1  
Restricted stock units | 2010 Plan    
Additional Employee Stock Plans Information    
Compensation expenses recognized $ 760 929
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest $ 1,808  
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 $ 343 $ 742
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