Tax Effect of Temporary Differences That Give Rise to Deferred Tax Assets and Deferred Tax Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 27, 2014	Dec. 28, 2013
Deferred tax assets:
Self-insurance reserves	$ 120,965	$ 118,276
Retirement plan contributions	55,673	53,299
Postretirement benefit cost	42,733	41,384
Reserves not currently deductible	23,326	11,760
Leases	21,374	22,890
Purchase allowances	16,717	10,303
Inventory capitalization	14,437	13,178
Other	1,533	1,323
Total deferred tax assets	296,758	272,413
Deferred tax liabilities:
Property, plant and equipment, primarily due to depreciation	528,469	507,308
Investment valuation	69,777	56,358
Other	16,037	9,942
Total deferred tax liabilities	$ 614,283	$ 573,608