Accrued Expenses and Other Current Liabilities (Product Warranty Rollforward) (Details) (USD $)	3 Months Ended
	Oct. 31, 2011	Oct. 31, 2010
Accrued Expenses and Other Current Liabilities [Abstract]
Accrued warranty obligations, as of the beginning of the period	$ 9,120,000	$ 10,562,000
Provision for warranty obligations	1,624,000	1,799,000
Reversal of warranty liability	0	(525,000)
Charges incurred	(1,461,000)	(1,946,000)
Accrued warranty obligations, as of the end of the period	$ 9,283,000	$ 9,890,000