Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Aug. 25, 2012	Aug. 27, 2011
Current liabilities [Abstract]
Payroll and benefit related	$ 31,825	$ 28,362
Insurance related	35,374	32,836
Environmental related	5,100	4,174
Other	8,176	11,258
Total current accrued liabilities	80,475	76,630
Long-term liabilities [Abstract]
Benefit related	18,380	16,016
Environmental related	14,920	14,194
Asset retirement obligations	10,120	9,488
Total long-term accrued liabilities	43,420	39,698
Total accrued liabilities	$ 123,895	$ 116,328