v3.5.0.2

Stock-Based Compensation (Tables) | 9 Months Ended
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Sep. 30, 2016
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 nine months and quarters ended September 30, 2016 and 2015.
|  | Quarter Ended September 30, |  |  | Nine Months Ended September 30, |
|  | 2016 |  |  | 2015 |  |  | 2016 |  |  | 2015 |
|  | (Thousands of dollars) |
Stock-based compensation expense: |  |  |  |
Time-based restricted stock units |  | $ | 631 |  |  | $ | 619 |  |  | $ | 1,847 |  |  | $ | 1,827 |
Performance-based restricted stock units |  |  | 823 |  |  |  | 1,081 |  |  |  | 2,502 |  |  |  | 3,232 |
Total stock-based compensation expense |  | $ | 1,454 |  |  | $ | 1,700 |  |  | $ | 4,349 |  |  | $ | 5,059 |

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