Description of Business and Summary of Significant Accounting Policies - Summary of Change in Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Jul. 31, 2012		Jul. 31, 2011		Jul. 31, 2010
Accounting Policies [Line Items]
Allowance for doubtful accounts, Balance at beginning of year	$ 15,375		$ 12,458		$ 15,579
Allowance for doubtful accounts, Additions charged to costs and expenses	2,098		3,310		3,769
Allowance for doubtful accounts, Deductions	(4,418)	[1]	(393)	[1]	(6,890)	[1]
Allowance for doubtful accounts, Balance at end of year	$ 13,055		$ 15,375		$ 12,458

[1] Primarily uncollectible accounts written off, net of recoveries.