Restructuring charges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Nov. 30, 2012	Nov. 30, 2011
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	$ 10,700
Total Charges to Date	6,605
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	2,955
Charges	1,593	0
Payments and Other	(3,300)
Restructuring reserve, ending balance	1,248
Severance costs [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	4,000
Total Charges to Date	3,680
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	2,477
Charges	939
Payments and Other	(2,548)
Restructuring reserve, ending balance	868
Contract termination costs [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	4,100
Total Charges to Date	445
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	414
Charges	5
Payments and Other	(59)
Restructuring reserve, ending balance	360
Other exit costs [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	2,600
Total Charges to Date	2,480
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	64
Charges	649
Payments and Other	(693)
Restructuring reserve, ending balance	20
Metal Recycling Business [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	2,400
Total Charges to Date	2,209
Restructuring Reserve [Roll Forward]
Charges	550
Auto Parts Business [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	600
Total Charges to Date	420
Restructuring Reserve [Roll Forward]
Charges	187
Unallocated (Corporate) [Member]
Restructuring Cost and Reserve [Line Items]
Total Expected Charges	7,700
Total Charges to Date	3,976
Restructuring Reserve [Roll Forward]
Charges	$ 856