Pensions and Other Postretirement Benefits (Tables)

9 Months Ended

Jan. 25, 2012

Compensation and Retirement Disclosure [Abstract]

Components of net periodic benefit cost

	Third Quarter Ended
	January 25, 2012			January 26, 2011			January 25, 2012			January 26, 2011
	Pension Benefits						Other Retiree Benefits
	(Thousands of Dollars)
Service cost	$	8,262		$	8,169		$	1,478		$	1,581
Interest cost	34,273			35,806			2,844			3,184
Expected return on plan assets	(57,665		)	(57,745		)	—			—
Amortization of prior service cost/(credit)	493			622			(1,533		)	(1,288		)
Amortization of unrecognized loss	20,691			19,536			274			401
Settlement charge	—			861			—			—
Net periodic benefit cost	$	6,054		$	7,249		$	3,063		$	3,878

	Nine Months Ended
	January 25, 2012			January 26, 2011			January 25, 2012			January 26, 2011
	Pension Benefits						Other Retiree Benefits
	(Thousands of Dollars)
Service cost	$	25,318		$	24,002		$	4,475		$	4,709
Interest cost	104,759			105,597			8,591			9,500
Expected return on plan assets	(176,202		)	(170,315		)	—			—
Amortization of prior service cost/(credit)	1,486			1,830			(4,595		)	(3,869		)
Amortization of unrecognized loss	62,857			57,892			821			1,203
Settlement charge	—			861			—			—
Net periodic benefit cost	$	18,218		$	19,867		$	9,292		$	11,543