Income Taxes (Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 25, 2010
Deferred tax assets:
Self-insurance reserves	$ 114,522	$ 113,557
Retirement plan contributions	48,825	44,686
Postretirement benefit cost	41,515	36,551
Reserves not currently deductible	18,047	24,731
Inventory capitalization	11,687	12,650
Advance purchase allowances	6,454	7,768
Other	4,357	9,378
Total deferred tax assets	245,407	249,321
Deferred tax liabilities:
Property, plant and equipment, primarily due to depreciation	491,485	409,736
Other	11,324	6,154
Total deferred tax liabilities	$ 502,809	$ 415,890