Commitments, Guarantees, and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended		12 Months Ended			1 Months Ended	12 Months Ended		1 Months Ended		1 Months Ended	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012 Minimum	Jul. 31, 2012 Maximum	Jul. 31, 2011 Maximum	Oct. 11, 2011 Credit Agreement	Jul. 31, 2012 Credit Agreement	Jul. 31, 2011 Credit Agreement	Oct. 11, 2011 Credit Agreement Minimum	Jul. 31, 2012 Credit Agreement Minimum	Oct. 11, 2011 Credit Agreement Maximum	Jul. 31, 2012 Credit Agreement Maximum	Jul. 31, 2012 Credit Agreement Other Revolving Credit Facilities	Oct. 11, 2011 Credit Agreement LIBOR Rate Minimum	Oct. 11, 2011 Credit Agreement LIBOR Rate Maximum	Oct. 11, 2011 Credit Agreement Defined Base Rate Minimum	Oct. 11, 2011 Credit Agreement Defined Base Rate Maximum	Oct. 11, 2011 Credit Agreement Federal Funds Rate	Oct. 11, 2011 Credit Agreement One Month London Inter Bank Offer Rate	Jul. 31, 2012 Product Extended Warranty Contracts	Jul. 31, 2011 Product Extended Warranty Contracts
Commitments and Contingencies Disclosure [Line Items]
Standard product warranty term			12 months	26 months
Deferred revenue for product extended warranty contracts	$ 12,267,000	$ 8,289,000																		$ 7,207,000	$ 6,528,000
Credit facility maximum borrow capacity						100,000,000
Revolving credit agreement period						5 years
Credit facility terminated amount						20,000,000
Percentage of capital stock pledge as collateral						65.00%
Aggregate available credit amount under specified circumstances						150,000,000
Variable interest rate														1.25%	2.00%	0.00%	1.00%	0.50%	1.00%
Credit facility commitment fee percentage									0.20%		0.35%
Leverage ratio of total debt to earnings before interest tax depreciation amortization												2.75
Interest coverage ratio										3
Leverage ratio							0.006
Credit facility transaction costs incurred							500,000
Credit facility, maturity period							5 years
Credit facility available borrow capacity													4,000,000
Line of credit amount outstanding							0	0
Percentage of revenue				1.30%	1.00%
Employee termination costs	400,000
Business exit cost	$ 1,288,000