Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 quarters ended March 31, 2017 and 2016.

	Quarter Ended
	March 31,
	2017		2016
	(Thousands of dollars)
Stock-based compensation expense:
Time-based restricted stock units	$	553	$	619
Performance-based restricted stock units		—		871
Total stock-based compensation expense	$	553	$	1,490