v3.7.0.1
Stock-Based Compensation (Tables)
6 Months Ended
Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Summary of Share Based Compensation Expense
The table below sets forth the total amount of stock-based compensation expense for the six months and quarter ended June 30, 2017 and 2016
 
 
Quarter Ended  
 June 30,
 
Six Months Ended 
 June 30,
 
 
2017
 
2016
 
2017
 
2016
 
 
(Thousands of dollars)
Stock-based compensation expense:
 
 
 
 
 
 
Time-based restricted stock units
 
$
556

 
$
597

 
$
1,111

 
$
1,216

Performance-based restricted stock units
 
705

 
809

 
705

 
1,680

Total stock-based compensation expense
 
$
1,261

 
$
1,406

 
$
1,816

 
$
2,896