Pension and Postretirement Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 25, 2011	Sep. 30, 2012	Sep. 25, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions to defined benefit pension plans			$ 5,500
Expected contributions during the remainder of fiscal year	1,600		1,600
Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1,001	1,023	3,280	3,192
Interest cost	5,104	5,144	15,650	15,598
Expected return on assets	(5,377)	(6,172)	(16,280)	(18,679)
Net amortization and deferrals	1,788	1,288	5,457	3,878
Curtailment loss	673	0	673	0
Net periodic benefit cost	3,189	1,283	8,780	3,989
Postretirement [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	183	171	551	513
Interest cost	440	440	1,320	1,320
Expected return on assets	0	0	0	0
Net amortization and deferrals	20	18	60	54
Curtailment loss	0	0	0	0
Net periodic benefit cost	$ 643	$ 629	$ 1,931	$ 1,887