Schedule of Major Classifications of Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2014	Jul. 31, 2014
Inventory [Line Items]
Raw materials	$ 127,822	$ 122,150
Chassis	41,357	45,231
Work in process	49,068	49,537
Finished goods	31,592	27,424
Total	249,839	244,342
Excess of FIFO costs over LIFO costs	(27,988)	(27,988)
Total inventories	$ 221,851	$ 216,354