Employee and Retiree Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2014

Compensation And Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Expense

The table that follows provides the components of net periodic benefit expense for the three-month periods ended March 31, 2014 and 2013.

	Three Months Ended March 31,
							Other
	Pension Benefits						Postretirement Benefits
(Thousands of dollars)	2014			2013			2014			2013
Service cost	$	6,556			7,603			672			1,167
Interest cost		8,215			6,431			1,278			1,234
Expected return on plan assets		(8,480	)		(5,700	)		0			0
Amortization of prior service cost		225			276			(21	)		(42	)
Amortization of transitional liability		208			120			1			2
Recognized actuarial loss		1,733			3,532			59			457
Net periodic benefit expense	$	8,457			12,262			1,989			2,818