Fire at Bus Production Facility - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended			24 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2011
Fire At Bus Production Facility
Amount deductible per the policy	$ 5,000
Insurance proceeds received		10,203	13,313
Insurance recoveries recognized		10,437	18,079	28,516
Insurance proceeds which included for business interruption		6,315
Insurance recoveries, net of deductibles			13,079
Advances recorded as deferred revenue			234
Insurance proceeds recognized in current year, previously deferred		234
Gain on involuntary conversion		9,417	7,593	17,010
Cost incurred to reconstruct the Facility		$ 5,460		$ 6,943