Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Aug. 31, 2011
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	$ 1,986,820	$ 1,775,092
Net sales	1,986,820	1,775,092
Adjusted operating profit (loss)	47,675	40,698
Total assets	3,506,653	3,629,614	3,683,131
Corporate [Member]
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	60	6,258
Net sales	60	6,258
Adjusted operating profit (loss)	(23,268)	(10,603)
Total assets	1,511,870	1,075,944
Business Intersegment, Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment sales	(279,561)	(193,203)
Net sales	(279,561)	(193,203)
Adjusted operating profit (loss)	(6,145)	303
Total assets	(1,051,027)	(347,167)
Americas Recycling [Member]
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	373,393	347,169
Intersegment sales	41,412	28,626
Net sales	414,805	375,795
Adjusted operating profit (loss)	20,816	8,192
Total assets	242,769	251,332
Americas Mills [Member]
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	344,566	280,781
Intersegment sales	180,930	154,616
Net sales	525,496	435,397
Adjusted operating profit (loss)	57,931	34,143
Total assets	652,211	612,574
Americas Fabrication [Member]
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	315,517	283,943
Intersegment sales	4,251	3,810
Net sales	319,768	287,753
Adjusted operating profit (loss)	(7,380)	(22,008)
Total assets	585,007	593,596
International Mills [Member]
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	252,921	216,533
Intersegment sales	43,260	653
Net sales	296,181	217,186
Adjusted operating profit (loss)	9,822	6,433
Total assets	595,501	726,837
International Marketing and Distribution [Member]
Segment Reporting Information [Line Items]
Net sales-unaffiliated customers	700,363	640,408
Intersegment sales	9,708	5,498
Net sales	710,071	645,906
Adjusted operating profit (loss)	(4,101)	24,238
Total assets	$ 970,322	$ 716,498