Marketable Securities (Details 2) - USD ($) $ in Thousands	Jan. 31, 2016	Jul. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses	$ 250	$ 587
Fair Value	18,682	13,284
Mutual funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses	231	18
Fair Value	4,832	4,982
Corporate bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses	11
Fair Value	1,083
Certificates Of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses	7	2
Fair Value	11,217	2,194
International agency notes [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses		1
Fair Value		1,119
Straight Path Communications Inc. common stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses		563
Fair Value		1,523
Municipal Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Unrealized Losses	1	3
Fair Value	$ 1,550	$ 3,466