Segments' Internal Financial Reports (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2012		Aug. 31, 2011		Aug. 31, 2010
Segment Reporting Information [Line Items]
Revenues	$ 443,534	$ 507,797	$ 458,186	$ 398,199	$ 442,736	$ 317,280	$ 284,340	$ 198,934	$ 1,807,716	[1]	$ 1,243,290	[1]	$ 756,280	[1]
Gross Profit	54,539	61,938	51,486	46,457	51,075	38,150	26,650	23,656	214,420		139,531		101,998
Assets	1,384,544				1,301,655				1,384,544		1,301,655		1,072,888
Depreciation and amortization									42,371		38,293		37,511
Capital expenditures									117,885		84,302		38,989
Manufacturing
Segment Reporting Information [Line Items]
Revenues									1,370,900		770,596		305,333
Gross Profit									131,580		59,975		27,171
Assets	402,976				423,295				402,976		423,295		205,863
Depreciation and amortization									11,754		9,853		11,061
Capital expenditures									33,313		20,016		8,715
Wheel Services, Refurbishment and Parts
Segment Reporting Information [Line Items]
Revenues									498,336		492,355		402,694
Gross Profit									48,324		47,416		43,912
Assets	413,013				400,643				413,013		400,643		387,356
Depreciation and amortization									13,265		11,853		11,435
Capital expenditures									11,248		20,087		12,215
Leasing and Services
Segment Reporting Information [Line Items]
Revenues									90,538		70,498		73,190
Gross Profit									34,516		32,140		30,915
Assets	508,539				424,839				508,539		424,839		377,761
Depreciation and amortization									17,352		16,587		15,015
Capital expenditures									73,324		44,199		18,059
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenues									(152,058)		(90,159)		(24,937)
Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Assets	$ 60,016				$ 52,878				$ 60,016		$ 52,878		$ 101,908

[1] Revenue is presented on the basis of geographic location of customers.