Commitments and Contigencies (Details) (USD $)	12 Months Ended
Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2009
Operating Leases, Future Minimum Payments Due
Total rental expense	$ 45,900,000	$ 48,900,000	$ 68,400,000
Environmental remediation cost	1,000,000	1,100,000
Total environmental liabilities	16,300,000	9,800,000
Long-term environmental liabilities	5,100,000	5,900,000
Equipment [Member]
Operating Leases, Future Minimum Payments Due
2012	13,891,000
2013	8,443,000
2014	4,224,000
2015	1,395,000
2016	706,000
Real Estate [Member]
Operating Leases, Future Minimum Payments Due
2012	22,398,000
2013	19,120,000
2014	17,100,000
2015	15,723,000
2016	$ 12,871,000

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Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable after twelve months or beyond the next operating cycle if longer.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

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