Segment Information - Segments Internal Financial Reports (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2018		Aug. 31, 2017		Aug. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 689,206	$ 641,387	$ 629,336	$ 559,535	$ 611,407	$ 439,161	$ 566,282	$ 552,314	$ 2,519,464	[1]	$ 2,169,164	[1]	$ 2,679,524	[1]
Earnings (loss) from operations	59,134	71,539	60,870	61,442	57,780	48,472	81,520	72,660	252,985		260,432		408,552
Assets	2,465,464				2,397,705				2,465,464		2,397,705		1,835,774
Depreciation and amortization									74,356		65,129		63,345
Capital expenditures									176,848		86,065		139,013
Manufacturing
Segment Reporting Information [Line Items]
Revenues	571,175	510,099	511,827	451,485	508,547	317,104	445,504	454,033	2,044,586		1,725,188		2,096,331
Earnings (loss) from operations									240,901		295,334		415,094
Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenues	85,787	94,515	88,710	78,011	75,099	85,231	82,714	69,635	347,023		312,679		322,395
Earnings (loss) from operations									16,731		14,984		19,948
Leasing & Services
Segment Reporting Information [Line Items]
Revenues	32,244	$ 36,773	$ 28,799	$ 30,039	27,761	$ 36,826	$ 38,064	$ 28,646	127,855		131,297		260,798
Earnings (loss) from operations									88,481		31,904		51,723
Operating Segments | Manufacturing
Segment Reporting Information [Line Items]
Revenues									2,162,743		1,744,479		2,185,489
Earnings (loss) from operations									258,622		296,356		439,393
Assets	1,020,757				914,450				1,020,757		914,450		701,296
Depreciation and amortization									44,225		33,807		27,137
Capital expenditures									59,707		54,973		51,294
Operating Segments | Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenues									388,517		343,540		354,831
Earnings (loss) from operations									19,479		17,287		22,550
Assets	306,756				236,315				306,756		236,315		275,599
Depreciation and amortization									10,771		11,143		11,971
Capital expenditures									5,204		3,129		10,190
Operating Segments | Leasing & Services
Segment Reporting Information [Line Items]
Revenues									139,702		143,109		273,899
Earnings (loss) from operations									98,777		43,003		64,824
Assets	578,818				535,323				578,818		535,323		516,147
Depreciation and amortization									19,360		20,179		24,237
Capital expenditures									111,937		27,963		77,529
Operating Segments | Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Assets	$ 559,133				$ 711,617				559,133		711,617		342,732
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues									(171,498)		(61,964)		(134,695)
Earnings (loss) from operations									(30,765)		(14,424)		(40,002)
Intersegment Eliminations | Manufacturing
Segment Reporting Information [Line Items]
Revenues									(118,157)		(19,291)		(89,158)
Earnings (loss) from operations									(17,721)		(1,022)		(24,299)
Intersegment Eliminations | Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenues									(41,494)		(30,861)		(32,436)
Earnings (loss) from operations									(2,748)		(2,303)		(2,602)
Intersegment Eliminations | Leasing & Services
Segment Reporting Information [Line Items]
Revenues									(11,847)		(11,812)		(13,101)
Earnings (loss) from operations									(10,296)		(11,099)		(13,101)
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Earnings (loss) from operations									$ (93,128)		$ (81,790)		$ (78,213)

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