Acquisitions and Divestitures - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended				9 Months Ended			12 Months Ended	9 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2013 Precision Dynamics Corporation [Member]	Apr. 30, 2014 Precision Dynamics Corporation [Member]	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2014 Customer Relationships [Member]	Jul. 31, 2013 Customer Relationships [Member]	Apr. 30, 2014 Customer Relationships [Member] Precision Dynamics Corporation [Member]	Apr. 30, 2014 Trademarks [Member] Precision Dynamics Corporation [Member]
Business Acquisition [Line Items]
Proceeds from borrowing on notes payable for PDC Acquisition			$ 63,000	$ 220,000			$ 63,000	$ 220,000
Repayment of borrowing on notes payable			39,000	173,000			39,000
Customer relationships						102,500
Finite-Lived Intangible Asset, Useful Life									8 years	8 years	10 years	3 years
Finite-Lived Trade Names, Gross						6,800
Goodwill						168,150
Goodwill, Expected Tax Deductible Amount						57,374
Other Intangible Assets						109,300
Intangibles, Expected Tax Deductible						51,672
Acquisition Related Costs					3,600
Adjustment, Inventory					1,530
Interest expense	3,381	4,186	10,777	12,755	529
Income tax expense (benefit)	(4,074)	(6,202)	(17,077)	(48,340)	(135)
Amortization of Intangible Assets	$ 4,713	$ 5,007	$ 14,837	$ 11,020	$ 6,208