Schedule of Major Classifications of Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2013	Jul. 31, 2013
Inventory [Line Items]
Raw materials	$ 106,416	$ 99,154
Chassis	34,192	34,108
Work in process	41,046	36,188
Finished goods	41,875	9,888
Total	223,529	179,338
Excess of FIFO costs over LIFO costs	(26,302)	(26,302)
Total inventories	$ 197,227	$ 153,036