Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Jul. 31, 2013	Apr. 30, 2013
Contingent Consideration, Fair Value Disclosure	$ 9,100	$ 9,100
Fair Value, Inputs, Level 3 [Member]
Contingent Consideration, Fair Value Disclosure	9,100	9,100
Money Market [Member]
Cash equivalents measured at fair value	78,851	34,029	49,025
Money Market [Member] | Level 1 [Member]
Cash equivalents measured at fair value	78,851	34,029	49,025
Commercial Paper [Member]
Cash equivalents measured at fair value	630	630	630
Commercial Paper [Member] | Level 2 [Member]
Cash equivalents measured at fair value	630	630	630
Certificates of Deposit [Member]
Cash equivalents measured at fair value	630	630	630
Certificates of Deposit [Member] | Level 2 [Member]
Cash equivalents measured at fair value	$ 630	$ 630	$ 630