Employee and Retiree Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2012

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, 2012 and 2011.

	Three Months Ended March 31,
	Pension Benefits						Other Postretirement  Benefits
(Thousands of dollars)	2012			2011			2012			2011
Service cost	$	5,888			5,896			1,041			1,224
Interest cost		7,292			7,993			1,449			1,647
Expected return on plan assets		(6,305	)		(6,925	)		0			0
Amortization of prior service cost		312			344			(46	)		(64	)
Amortization of transitional (asset) liability		111			(51	)		2			2
Recognized actuarial net loss		3,767			2,576			489			753
Net periodic benefit expense	$	11,065			9,833			2,935			3,562