Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2015

Incentive Plans [Abstract]

Share-Based Plans, Amounts Recognized

	Nine Months Ended
	September 30,
(Thousands of dollars)		2015	2014
Compensation charged against income before tax benefit	$	30,722	45,373
Related income tax benefit recognized in income		9,046	14,036