Segments Internal Financial Reports (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 28, 2016	Nov. 30, 2015	Aug. 31, 2017		Aug. 31, 2016		Aug. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 611,407	$ 439,161	$ 566,282	$ 552,314	$ 595,190	$ 612,866	$ 669,079	$ 802,389	$ 2,169,164	[1]	$ 2,679,524	[1]	$ 2,605,278	[1]
Earnings (loss) from operations	57,780	48,472	81,520	72,660	83,545	84,129	92,393	148,485	260,432		408,552		386,892
Assets	2,397,705				1,835,774				2,397,705		1,835,774		1,787,452
Depreciation and amortization									65,129		63,345		45,156
Capital expenditures									86,065		139,013		105,989
Manufacturing
Segment Reporting Information [Line Items]
Revenues	508,547	317,104	445,504	454,033	484,645	458,494	454,531	698,661	1,725,188		2,096,331		2,136,051
Earnings (loss) from operations									295,334		415,094		396,921
Wheels & Parts
Segment Reporting Information [Line Items]
Revenues	75,099	85,231	82,714	69,635	74,791	78,417	90,458	78,729	312,679		322,395		371,237
Earnings (loss) from operations									14,984		19,948		27,563
Leasing & Services
Segment Reporting Information [Line Items]
Revenues	27,761	$ 36,826	$ 38,064	$ 28,646	35,754	$ 75,955	$ 124,090	$ 24,999	131,297		260,798		97,990
Earnings (loss) from operations									31,904		51,723		41,887
Operating Segments | Manufacturing
Segment Reporting Information [Line Items]
Revenues									1,744,479		2,185,489		2,143,585
Earnings (loss) from operations									296,356		439,393		397,716
Assets	914,450				701,296				914,450		701,296		675,409
Depreciation and amortization									33,807		27,137		20,668
Capital expenditures									54,973		51,294		84,354
Operating Segments | Wheels & Parts
Segment Reporting Information [Line Items]
Revenues									343,540		354,831		398,494
Earnings (loss) from operations									17,287		22,550		30,192
Assets	236,315				275,599				236,315		275,599		291,798
Depreciation and amortization									11,143		11,971		11,748
Capital expenditures									3,129		10,190		9,381
Operating Segments | Leasing & Services
Segment Reporting Information [Line Items]
Revenues									143,109		273,899		160,590
Earnings (loss) from operations									43,003		64,824		104,487
Assets	535,323				516,147				535,323		516,147		546,013
Depreciation and amortization									20,179		24,237		12,740
Capital expenditures									27,963		77,529		12,254
Operating Segments | Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Assets	$ 711,617				$ 342,732				711,617		342,732		274,232
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Earnings (loss) from operations									(81,790)		(78,213)		(79,479)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues									(61,964)		(134,695)		(97,391)
Earnings (loss) from operations									(14,424)		(40,002)		(66,024)
Intersegment Eliminations | Manufacturing
Segment Reporting Information [Line Items]
Revenues									(19,291)		(89,158)		(7,534)
Earnings (loss) from operations									(1,022)		(24,299)		(795)
Intersegment Eliminations | Wheels & Parts
Segment Reporting Information [Line Items]
Revenues									(30,861)		(32,436)		(27,257)
Earnings (loss) from operations									(2,303)		(2,602)		(2,629)
Intersegment Eliminations | Leasing & Services
Segment Reporting Information [Line Items]
Revenues									(11,812)		(13,101)		(62,600)
Earnings (loss) from operations									$ (11,099)		$ (13,101)		$ (62,600)

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