Discontinued Operations (Narrative) (Details) (USD $)	12 Months Ended			3 Months Ended	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010	Nov. 30, 2011 CMCS [Member]	Aug. 31, 2010 Joist and Deck Operations [Member]	Aug. 31, 2012 Joist and Deck Operations [Member] properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Severance expense	$ 25,600,000	$ 8,200,000	$ 21,500,000	$ 18,000,000	$ 11,700,000
Impairment charges of property, plant and equipment					26,800,000
Intangible asset and goodwill impairment					4,500,000
Inventory valuation adjustments	$ 13,917,000	$ 25,503,000	$ 53,203,000		$ 7,400,000
Number of remaining asset locations						2