Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2016

Incentive Plans [Abstract]

Share-Based Plans, Amounts Recognized

	Three Months Ended
	March 31,
(Thousands of dollars)		2016	2015
Compensation charged against income before tax benefit	$	9,988	16,315
Related income tax benefit recognized in income		3,251	5,100