Related Party Transactions - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended
	Apr. 30, 2010 Vehicle	Jun. 30, 2009	Aug. 31, 2012 Vehicle	Aug. 31, 2011
Related Party Transaction [Line Items]
Number of railcars owned			11,000
Value of railcars			$ 61,100,000
Carrying value of investment			8,301,000	5,769,000
Related party expenses for aircraft usage			200,000
WL Ross & Co., LLC (WL Ross)
Related Party Transaction [Line Items]
Secured term loan		75,000,000
Issuance of warrants to purchase Shares of Common Stock		3,401,095
Exercise price of common stock		$ 5.96
Term of warrants		5 years
Expiration date of term of warrants		2014-06
Percentage of participation		3.00%
Common Stock under the warrant agreement in which rights were transferred to purchase shares		101,337
Number of railcars owned	4,000
Value of railcars	256,000,000
Contract placement fee	6,100,000		900,000	800,000
Carrying value of investment			0
Number of railcars leased			400
Lease expense			3,100,000
Operating Leases, Future Minimum Payments Due			9,400,000
Schnitzer
Related Party Transaction [Line Items]
Sale of scrap metal			$ 9,200,000