Retirement and Benefit Plans (Components of Net Periodic Pension and Other Postretirement Benefit Costs) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 25, 2011	Jun. 26, 2010	Jun. 25, 2011	Jun. 26, 2010
Pension Benefits [Member]
Service cost	$ 634	$ 707	$ 1,273	$ 1,383
Interest cost	17,546	18,494	35,088	37,107
Expected return on plan assets	(20,098)	(20,872)	(40,203)	(41,747)
Recognized actuarial loss	4,325	3,273	8,752	6,619
Amortization of prior service costs and other	0	0		379
Net periodic benefit cost (income)	2,407	1,602	4,910	3,741
Other Benefits [Member]
Service cost	18	66	115	131
Interest cost	207	310	507	605
Expected return on plan assets	0	0
Recognized actuarial loss	26	64	110	112
Amortization of prior service costs and other	(1,002)	(1,002)	(2,004)	(2,003)
Net periodic benefit cost (income)	$ (751)	$ (562)	$ (1,272)	$ (1,155)