Guarantees, Commitments and Contingencies - Additional Information (Detail) - USD ($)				3 Months Ended
	Nov. 23, 2015	Nov. 23, 2011	Oct. 11, 2011	Oct. 31, 2016	Jul. 31, 2016
Commitments and Contingencies Disclosure [Line Items]
Liabilities related to agreements				$ 0
Revolving credit agreement period	5 years
Product Extended Warranty Contracts
Commitments and Contingencies Disclosure [Line Items]
Deferred revenue				$ 200,000	$ 200,000
Revolving Credit Facility Termination | Facility Exit Costs
Commitments and Contingencies Disclosure [Line Items]
Revolving credit agreement period			5 years
Credit facility maximum borrow capacity			$ 100,000,000
Credit facility, expiry date			Oct. 11, 2011
Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Credit facility maximum borrow capacity	$ 100,000,000
Credit facility, expiry date	Nov. 23, 2020
Leverage ratio				0.40%
Credit facility transaction costs incurred				$ 500,000
Credit facility, maturity period				5 years
Line of credit amount outstanding				$ 0	0
Revolving Credit Facility | Other Revolving Credit Facilities
Commitments and Contingencies Disclosure [Line Items]
Credit facility available borrowing capacity				$ 1,200,000	$ 1,200,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Standard product warranty term				12 months
Minimum | Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Credit facility commitment fee percentage		0.20%
Interest coverage ratio				300.00%
Minimum | Revolving Credit Facility | LIBOR Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		1.25%
Minimum | Revolving Credit Facility | Base Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		0.00%
Maximum
Commitments and Contingencies Disclosure [Line Items]
Standard product warranty term				60 months
Maximum | Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Aggregate available credit amount under specified circumstances	$ 200,000,000
Credit facility commitment fee percentage		0.35%
Leverage ratio of total debt to earnings before interest, taxes, depreciation, and amortization or EBITDA				275.00%
Maximum | Revolving Credit Facility | LIBOR Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		1.75%
Maximum | Revolving Credit Facility | Base Rate
Commitments and Contingencies Disclosure [Line Items]
Variable interest rate		1.00%