Investment in Unconsolidated Affiliates - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended
	Aug. 31, 2012 Vehicle	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2012 Vehicle	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2012 WLR-GBX	Aug. 31, 2011 WLR-GBX	Aug. 31, 2010 WLR-GBX	Apr. 30, 2010 WLR-GBX Vehicle	Aug. 31, 2012 Ohio Castings Llc	Jun. 30, 2003 Ohio Castings Llc
Investments in and Advances to Affiliates [Line Items]
Number of railcars owned	11,000								11,000						4,000
Value of railcars	$ 61,100,000								$ 61,100,000						$ 256,000,000
Contract placement fee					2,259,000					2,259,000					6,100,000
Share of losses	(317,000)	201,000	72,000	(372,000)	(1,273,000)	(539,000)	(575,000)	(587,000)	(416,000)	(2,974,000)	(1,601,000)	(2,100,000)	(2,500,000)	(1,400,000)
Carrying value of investment	8,301,000				5,769,000				8,301,000	5,769,000		0
Minority ownership interest																	33.00%
Intangibles and other assets	$ 81,368,000				$ 87,268,000				$ 81,368,000	$ 87,268,000						$ 7,700,000