Segment Information - Segments Internal Financial Reports (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020	Aug. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 295,622	$ 623,848	$ 698,611	$ 1,393,207
Earnings (loss) from operations	(25,727)	38,436	(27,841)	80,220
Assets	3,059,365		3,059,365		$ 3,173,834
Manufacturing
Segment Reporting Information [Line Items]
Revenue	202,094	489,943	510,816	1,147,310
Earnings (loss) from operations	(17,216)	46,105	(7,530)	99,248
Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenue	71,623	91,225	137,179	177,833
Earnings (loss) from operations	2,433	3,320	2,233	4,434
Leasing & Services
Segment Reporting Information [Line Items]
Revenue	21,905	42,680	50,616	68,064
Earnings (loss) from operations	6,420	12,793	12,310	22,570
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Earnings (loss) from operations	(17,364)	(23,782)	(34,854)	(46,032)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(5,141)	(20,394)	(30,698)	(28,091)
Earnings (loss) from operations	(720)	(14,217)	(7,501)	(15,141)
Intersegment Eliminations | Manufacturing
Segment Reporting Information [Line Items]
Revenue	2,425	21	23,016	118
Earnings (loss) from operations	100	1	2,605	(22)
Intersegment Eliminations | Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenue	1,603	5,133	1,904	10,984
Earnings (loss) from operations	(14)	(168)	(23)	(510)
Intersegment Eliminations | Leasing & Services
Segment Reporting Information [Line Items]
Revenue	1,113	15,240	5,778	16,989
Earnings (loss) from operations	634	14,384	4,919	15,673
Operating Segments
Segment Reporting Information [Line Items]
Earnings (loss) from operations	(17,364)	(23,782)	(34,854)	(46,032)
Operating Segments | Manufacturing
Segment Reporting Information [Line Items]
Revenue	204,519	489,964	533,832	1,147,428
Earnings (loss) from operations	(17,116)	46,106	(4,925)	99,226
Assets	1,313,819		1,313,819		1,301,715
Operating Segments | Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenue	73,226	96,358	139,083	188,817
Earnings (loss) from operations	2,419	3,152	2,210	3,924
Assets	277,788		277,788		271,862
Operating Segments | Leasing & Services
Segment Reporting Information [Line Items]
Revenue	23,018	57,920	56,394	85,053
Earnings (loss) from operations	7,054	$ 27,177	17,229	$ 38,243
Assets	851,546		851,546		739,025
Operating Segments | Unallocated, including cash
Segment Reporting Information [Line Items]
Assets	$ 616,212		$ 616,212		$ 861,232