Investments And Fair Value Measurements (Financial Assets Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2012	Jul. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	$ 156,206	$ 215,435
Auction Rate Securities	1,619	2,042
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	156,206	215,435
Auction Rate Securities
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents
Auction Rate Securities
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents
Auction Rate Securities	$ 1,619	$ 2,042