Asset Retirement Obligations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Nov. 26, 2011	Nov. 27, 2010
Rollforward of asset retirement liabilities [Abstract]
Beginning balance	$ 9,488
Accretion expense	158	147
Ending balance	$ 9,646

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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