Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2012
Allowance for Doubtful Accounts, Current [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 6,183	$ 7,137	$ 7,931	$ 6,005
Additions charged to expense	1,593	1,287	2,005
Due to acquired businesses	159	52	80
Deductions bad debts inventory written offs, net of recoveries	1,930	2,293	2,879
Inventory Valuation Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	13,009	15,944	22,288	11,316
Additions charged to expense	2,200	3,750	1,646
Due to acquired businesses	445	632	129
Deductions bad debts inventory written offs, net of recoveries	$ 4,338	$ 7,317	$ 8,119