Schedule of Major Classifications of Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014	Jul. 31, 2013
Inventory [Line Items]
Raw materials	$ 114,780	$ 99,154
Chassis	42,532	34,108
Work in process	50,936	36,188
Finished goods	40,440	9,888
Total	248,688	179,338
Excess of FIFO costs over LIFO costs	(26,752)	(26,302)
Total inventories	$ 221,936	$ 153,036