Valuation and Qualifying Accounts and Reserves (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended							12 Months Ended
	Jul. 31, 2012 Inventory Reserves [Member]	Jul. 31, 2011 Inventory Reserves [Member]	Jul. 31, 2010 Inventory Reserves [Member]	Jul. 31, 2012 Valuation Allowance On Income Taxes [Member]	Jul. 31, 2011 Valuation Allowance On Income Taxes [Member]	Jul. 31, 2010 Valuation Allowance On Income Taxes [Member]	Jul. 31, 2009 Valuation Allowance On Income Taxes [Member]	Jul. 31, 2012 Trade Receivable Allowances [Member]	Jul. 31, 2011 Trade Receivable Allowances [Member]	Jul. 31, 2010 Trade Receivable Allowances [Member]
Balance at Beginning of Period	$ 1,552	$ 1,452	$ 1,455	$ 1,588	$ 1,588	$ 1,588	$ 1,588	$ 3,423	$ 2,259	$ 1,877
Charged to Costs and Expenses	1,914	2,389	2,310					2,456	2,246	1,328
Deductions	(1,602)	(2,289)	(2,313)					(1,326)	(1,082)	(946)
Balance at End of Period	$ 1,864	$ 1,552	$ 1,452	$ 1,588	$ 1,588	$ 1,588	$ 1,588	$ 4,553	$ 3,423	$ 2,259