Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 29, 2012	Dec. 31, 2011
Income Taxes [Abstract]
Accounts receivable	$ 426	$ 403
Compensated absences	510	495
Long term employment incentives	2,891	1,554
Employee benefit plans	3,784	3,496
General liability insurance	1,113	1,074
Postretirement benefit obligations	6,255	5,931
Net operating loss carryforwards	6,535	6,825
Total deferred tax assets	21,514	19,778
Inventories	(6,241)	(5,511)
Unrealized gains on marketable securities	(3,506)	(3,799)
Nondeductible accruals and other	(1,995)	(1,021)
Depreciation	(102,301)	(86,658)
Total deferred tax liabilities	(114,043)	(96,989)
Net deferred tax liability	(92,529)	(77,211)
Current deferred tax liability - net	(3,420)	(4,130)
Noncurrent deferred tax liability - net	$ (89,109)	$ (73,081)