Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Additional Information (Details)

v3.7.0.1
Stock Based Compensation - Additional Information (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2017
USD ($)
age
shares
Mar. 31, 2016
USD ($)
Performance Share Unit Awards | 2010 Plan    
Additional Employee Stock Plans Informatioin    
Vesting period of awards 2 years  
Compensation expenses recognized $ 151 $ 127
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest 1,694  
Restricted Stock Unit Awards    
Additional Employee Stock Plans Informatioin    
Compensation expenses recognized 1,198 1,086
Unrecognized compensation expense, net of expected forfeitures, calculated under the fair value method for shares expected to vest $ 954  
Restricted Stock Unit Awards | Non-employee director    
Additional Employee Stock Plans Informatioin    
Number of shares issued upon exercise of units other than options | shares 1  
Restricted Stock Unit Awards | Management    
Additional Employee Stock Plans Informatioin    
Minimum age of employee, attaining which awards are continued to be vested upon retirement | age 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 | age 55  
Accelerated stock based compensation expense $ 619 $ 528
Restricted Stock Unit Awards | Common Stock | Management    
Additional Employee Stock Plans Informatioin    
Number of shares issued upon exercise of units other than options | shares 1  
Restricted Stock Unit Awards | 2010 Plan    
Additional Employee Stock Plans Informatioin    
Maximum period following a termination of service in which the share-based award will be settled 2 months 15 days