Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2016

Incentive Plans [Abstract]

Share-Based Plans, Amounts Recognized

	Six Months Ended
	June 30,
(Thousands of dollars)		2016	2015
Compensation charged against income before tax benefit	$	24,288	31,230
Related income tax benefit recognized		8,210	9,691