Segment Information - Segments Internal Financial Reports (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019	Aug. 31, 2019
Segment Reporting Information [Line Items]
Revenue	$ 623,848	$ 658,671	$ 1,393,207	$ 1,263,194
Earnings (loss) from operations	38,436	18,054	80,220	54,508
Assets	2,947,660		2,947,660		$ 2,990,637
Manufacturing
Segment Reporting Information [Line Items]
Revenue	489,943	476,019	1,147,310	947,808
Earnings (loss) from operations	46,105	13,990	99,248	50,845
Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenue	91,225	125,278	177,833	233,821
Earnings (loss) from operations	3,320	2,823	4,434	6,070
Leasing & Services
Segment Reporting Information [Line Items]
Revenue	42,680	57,374	68,064	81,565
Earnings (loss) from operations	12,793	21,030	22,570	38,543
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Earnings (loss) from operations	(23,782)	(19,789)	(46,032)	(40,950)
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue	(20,394)	(58,624)	(28,091)	(86,805)
Earnings (loss) from operations	(14,217)	(3,601)	(15,141)	(9,798)
Intersegment Eliminations | Manufacturing
Segment Reporting Information [Line Items]
Revenue	21	46,855	118	53,056
Earnings (loss) from operations	1	2,358	(22)	2,791
Intersegment Eliminations | Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenue	5,133	8,858	10,984	24,839
Earnings (loss) from operations	(168)	(858)	(510)	(546)
Intersegment Eliminations | Leasing & Services
Segment Reporting Information [Line Items]
Revenue	15,240	2,911	16,989	8,910
Earnings (loss) from operations	14,384	2,101	15,673	7,553
Operating Segments
Segment Reporting Information [Line Items]
Earnings (loss) from operations	(23,782)	(19,789)	(46,032)	(40,950)
Operating Segments | Manufacturing
Segment Reporting Information [Line Items]
Revenue	489,964	522,874	1,147,428	1,000,864
Earnings (loss) from operations	46,106	16,348	99,226	53,636
Assets	1,535,118		1,535,118		1,606,571
Operating Segments | Wheels, Repair & Parts
Segment Reporting Information [Line Items]
Revenue	96,358	134,136	188,817	258,660
Earnings (loss) from operations	3,152	1,965	3,924	5,524
Assets	314,069		314,069		306,725
Operating Segments | Leasing & Services
Segment Reporting Information [Line Items]
Revenue	57,920	60,285	85,053	90,475
Earnings (loss) from operations	27,177	$ 23,131	38,243	$ 46,096
Assets	897,745		897,745		708,799
Operating Segments | Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Assets	$ 200,728		$ 200,728		$ 368,542