Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 26, 2015	Dec. 27, 2014
Income Taxes [Abstract]
Accounts receivable	$ 813	$ 615
Compensated absences	983	362
Long term employment incentives	3,143	1,161
Employee benefit plans	10,485	10,734
General liability insurance	4,048	3,655
Postretirement benefit obligations	5,906	7,676
Net operating loss carryforwards	5,926	6,218
Other	2,173	1,359
Total deferred tax assets	33,477	31,780
Inventories	(6,808)	(7,459)
Unrealized gains on marketable securities	(3,323)	(3,371)
Nondeductible accruals and other	(9,240)	(6,522)
Depreciation	(111,126)	(111,708)
Total deferred tax liabilities	(130,497)	(129,060)
Net deferred tax liability	$ (97,020)	$ (97,280)