Guarantees, Commitments and Contingencies - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended						0 Months Ended	3 Months Ended				3 Months Ended	0 Months Ended		0 Months Ended		3 Months Ended	0 Months Ended	3 Months Ended		0 Months Ended
	Oct. 11, 2011	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014 Product Extended Warranty Contracts	Jul. 31, 2014 Product Extended Warranty Contracts	Oct. 31, 2014 Other Liabilities	Jul. 31, 2014 Other Liabilities	Oct. 11, 2011 Revolving Credit Facility	Oct. 31, 2014 Revolving Credit Facility	Jul. 31, 2014 Revolving Credit Facility	Oct. 11, 2011 Revolving Credit Facility	Oct. 31, 2014 Revolving Credit Facility Other Revolving Credit Facilities	Oct. 31, 2014 Minimum	Oct. 11, 2011 Minimum Revolving Credit Facility	Oct. 31, 2014 Minimum Revolving Credit Facility	Oct. 11, 2011 Minimum Revolving Credit Facility LIBOR Rate	Oct. 11, 2011 Minimum Revolving Credit Facility Base Rate	Oct. 31, 2014 Maximum	Oct. 11, 2011 Maximum Revolving Credit Facility	Oct. 31, 2014 Maximum Revolving Credit Facility	Oct. 11, 2011 Maximum Revolving Credit Facility	Oct. 11, 2011 Maximum Revolving Credit Facility LIBOR Rate	Oct. 11, 2011 Maximum Revolving Credit Facility Base Rate
Commitments and Contingencies Disclosure [Line Items]
Liabilities related to agreements		$ 0
Standard product warranty term													12 months					60 months
Deferred revenue for product extended warranty contracts				6,600,000	7,400,000
Revolving credit agreement period	5 years
Credit facility maximum borrow capacity											100,000,000
Credit facility, expiry date								Oct. 10, 2016
Aggregate available credit amount under specified circumstances																					150,000,000
Percentage of capital stock pledge as collateral											65.00%
Variable interest rate																1.25%	0.00%					2.00%	1.00%
Credit facility commitment fee percentage														0.20%					0.35%
Leverage ratio of total debt to earnings before interest, taxes, depreciation, and amortization or EBITDA																				275.00%
Interest coverage ratio															300.00%
Leverage ratio									0.003%
Credit facility transaction costs incurred									500,000
Credit facility, maturity period									5 years
Credit facility available borrowing capacity												1,400,000
Line of credit amount outstanding									0	0
Asset retirement obligations, estimated cost of restoring our leased facilities						1,100,000	1,100,000
Business exit cost		$ 800,000	$ 300,000