Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		3 Months Ended		1 Months Ended			3 Months Ended
	Nov. 30, 2012	May 31, 2012	Nov. 30, 2012 Mexican Joint Venture Credit Facility	Nov. 30, 2012 Seb Finans Ab Vehicle	Mar. 31, 2004 Okombi GmbH	Nov. 30, 2012 Okombi GmbH Vehicle	Jan. 31, 2000 Okombi GmbH Vehicle	Nov. 30, 2012 Minimum Y	Nov. 30, 2012 Maximum Y	Nov. 30, 2012 Additional Investigation Year	Nov. 30, 2012 Portland Harbor Site Minimum	Nov. 30, 2012 Portland Harbor Site Maximum	Nov. 30, 2012 Area Of Willamette River Adjacent to the Company's Portland, Oregon Manufacturing Facility Minimum	Nov. 30, 2012 Area Of Willamette River Adjacent to the Company's Portland, Oregon Manufacturing Facility Maximum
Commitments and Contingencies Disclosure [Line Items]
Remedial investigation and feasibility study	$ 90
Remedial investigation and feasibility study, period	11 years									2 years
Period for remedial action								2	28
Cleanup expenses											169	1,800	9	163
Number of installed railcar				372
Value of railcars	77.0	61.1		20.0
Settlement agreement effective date				2007-02-28	March 2004
Number of freight cars to build							201
Number of vehicles required to be removed from service						201
Bank and third party warranty guarantee facilities	1.9
Debt outstanding			45.7
Guarantee obligations			37.8
Contribution to Capital expenditure for fourth manufacturing line commitment			10.0
Percentage of commitment Contribution by company towards fourth Manufacturing line			50.00%
Amount contributed by company and the joint venture partner for capital expenditure of fourth manufacturing line			2.5
Outstanding letters of credit	$ 5.6