Restructuring charges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			$ 12,600
Total Charges to Date			8,145
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			2,955
Charges	1,540	0	3,133	0
Payments and Other			(4,977)
Restructuring reserve, ending balance	1,111		1,111
Severance costs
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			4,900
Total Charges to Date			3,796
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			2,477
Charges			1,055
Payments and Other			(3,034)
Restructuring reserve, ending balance	498		498
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			3,500
Total Charges to Date			464
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			414
Charges			24
Payments and Other			(193)
Restructuring reserve, ending balance	245		245
Other exit costs
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			4,200
Total Charges to Date			3,885
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			64
Charges			2,054
Payments and Other			(1,750)
Restructuring reserve, ending balance	368		368
Metal Recycling Business [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			3,000
Total Charges to Date			2,270
Restructuring Reserve [Roll Forward]
Charges			610
Auto Parts Business [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			500
Total Charges to Date			444
Restructuring Reserve [Roll Forward]
Charges			211
Unallocated (Corporate)
Restructuring Cost and Reserve [Line Items]
Total Expected Charges			9,100
Total Charges to Date			5,431
Restructuring Reserve [Roll Forward]
Charges			$ 2,312