Retirement plans (Tables) (Pension Plans, Defined Benefit [Member])

6 Months Ended

Jun. 30, 2013

Pension Plans, Defined Benefit [Member]

Defined Benefit Plan Disclosure [Line Items]

Benefit costs

The Company’s retirement plan costs, which include costs for qualified and nonqualified plans, are presented in the following table:

In thousands of dollars	Thirteen Weeks Ended						Twenty-six Weeks Ended
	Jun. 30, 2013			Jun. 24, 2012			Jun. 30, 2013			Jun. 24, 2012
Service cost-benefits earned during the period	$	1,756		$	1,747		$	3,881		$	3,779
Interest cost on benefit obligation	35,071			38,077			70,254			77,731
Expected return on plan assets	(49,299		)	(47,145		)	(98,842		)	(94,794		)
Amortization of prior service cost	1,898			1,917			3,776			3,845
Amortization of actuarial loss	16,190			12,919			31,550			26,424
Expense for Company-sponsored retirement plans	5,616			7,515			10,619			16,985
Settlement charges	—			5,423			—			5,423
Total retirement plan cost	$	5,616		$	12,938		$	10,619		$	22,408