Discontinued Operations - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	0 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 21, 2013	Feb. 28, 2014	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of bus business	$ 100,000					$ 105,043
Discontinued operation, amounts collected from ASV		5,043
Pre-tax gain (loss) on disposal of discontinued business						7,079
Impact of indemnification to tax expenses				1,883		1,883
Income tax benefit (expense)			$ 573	$ 713	$ 1,677	$ 1,886