Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2015

Incentive Plans [Abstract]

Share-Based Plans, Amounts Recognized

	Six Months Ended
	June 30,
(Thousands of dollars)	2015		2014
Compensation charged against income before tax benefit	$	31,230		32,142
Related income tax benefit recognized in income		9,691		9,978