Segments Internal Financial Reports (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Aug. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 495,058	$ 490,355
Earnings (loss) from operations	54,422	38,222
Assets	1,569,382		1,517,168
Manufacturing
Segment Reporting Information [Line Items]
Revenues	379,949	359,473
Wheels & Parts
Segment Reporting Information [Line Items]
Revenues	86,624	113,401
Leasing & Services
Segment Reporting Information [Line Items]
Revenues	28,485	17,481
External Customers
Segment Reporting Information [Line Items]
Revenues	495,058	490,355
Earnings (loss) from operations	54,422	38,222
Operating Segments | Manufacturing
Segment Reporting Information [Line Items]
Revenues	387,369	359,473
Earnings (loss) from operations	52,837	38,314
Assets	585,240		521,711
Operating Segments | Wheels & Parts
Segment Reporting Information [Line Items]
Revenues	93,535	115,054
Earnings (loss) from operations	8,716	(343)
Assets	301,300		298,009
Operating Segments | Leasing & Services
Segment Reporting Information [Line Items]
Revenues	41,669	20,350
Earnings (loss) from operations	24,226	11,539
Assets	493,048		436,075
Operating Segments | Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Assets	189,794		261,373
Operating Segments | External Customers | Manufacturing
Segment Reporting Information [Line Items]
Revenues	379,949	359,473
Earnings (loss) from operations	52,051	38,314
Operating Segments | External Customers | Wheels & Parts
Segment Reporting Information [Line Items]
Revenues	86,624	113,401
Earnings (loss) from operations	7,932	(374)
Operating Segments | External Customers | Leasing & Services
Segment Reporting Information [Line Items]
Revenues	28,485	17,481
Earnings (loss) from operations	11,042	8,670
Operating Segments | Inter Segment | Manufacturing
Segment Reporting Information [Line Items]
Revenues	7,420
Earnings (loss) from operations	786
Operating Segments | Inter Segment | Wheels & Parts
Segment Reporting Information [Line Items]
Revenues	6,911	1,653
Earnings (loss) from operations	784	31
Operating Segments | Inter Segment | Leasing & Services
Segment Reporting Information [Line Items]
Revenues	13,184	2,869
Earnings (loss) from operations	13,184	2,869
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(27,515)	(4,522)
Earnings (loss) from operations	(14,754)	(2,900)
Intersegment Eliminations | Inter Segment
Segment Reporting Information [Line Items]
Revenues	(27,515)	(4,522)
Earnings (loss) from operations	(14,754)	(2,900)
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Earnings (loss) from operations	(16,603)	(8,388)
Corporate, Non-Segment | External Customers
Segment Reporting Information [Line Items]
Earnings (loss) from operations	$ (16,603)	$ (8,388)