Guarantees, Commitments and Contingencies - Additional Information (Detail) - USD ($)			3 Months Ended		9 Months Ended
	Nov. 23, 2015	Nov. 23, 2011	Jan. 31, 2016	Jul. 31, 2015	Apr. 30, 2016	Apr. 30, 2015
Commitments and Contingencies Disclosure [Line Items]
Liabilities related to agreements					$ 0
Revolving credit agreement period	5 years
Business exit cost			$ 13,300,000	$ 1,600,000
Other Current Liabilities
Commitments and Contingencies Disclosure [Line Items]
Accrued business exit cost					14,900,000
General and Administrative
Commitments and Contingencies Disclosure [Line Items]
Business exit cost			10,100,000	1,000,000
Other Expense
Commitments and Contingencies Disclosure [Line Items]
Business exit cost			$ 3,200,000	600,000
Three Month
Commitments and Contingencies Disclosure [Line Items]
Accrued litigation charge					0	$ 300,000
Nine Month
Commitments and Contingencies Disclosure [Line Items]
Accrued litigation charge					200,000	$ 1,400,000
Product Extended Warranty Contracts
Commitments and Contingencies Disclosure [Line Items]
Deferred revenue for product extended warranty contracts				5,300,000	$ 5,900,000
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					1.00%
Credit facility transaction costs incurred					$ 500,000
Credit facility, maturity period					5 years
Line of credit amount outstanding					$ 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%