Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 28, 2013	Dec. 29, 2012
Income Taxes [Abstract]
Accounts receivable	$ 585	$ 426
Compensated absences	403	510
Long term employment incentives	2,785	2,891
Employee benefit plans	4,221	3,784
General liability insurance	1,223	1,113
Postretirement benefit obligations	7,037	6,255
Net operating loss carryforwards	5,736	6,535
Total deferred tax assets	21,990	21,514
Inventories	(6,809)	(6,241)
Unrealized gains on marketable securities	(2,753)	(3,506)
Nondeductible accruals and other	(4,745)	(1,995)
Depreciation	(109,836)	(102,301)
Total deferred tax liabilities	(124,143)	(114,043)
Net deferred tax liability	(102,153)	(92,529)
Current deferred tax liability - net	(4,219)	(3,420)
Noncurrent deferred tax liability - net	$ (97,934)	$ (89,109)