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Marketable Securities (Details) - USD ($) $ in Thousands | Jul. 31, 2018 | Jul. 31, 2017
--- | --- | ---
Available-for-sale securities: |  |
Amortized Cost | $ 6,006 | $ 58,238
Gross Unrealized Gains |  |
Gross Unrealized Gains, Total |  | 82
Gross Unrealized Losses, Total | (34) | (48)
Fair Value | 5,972 | 58,272
Certificates of deposit [Member] |  |
Available-for-sale securities: |  |
Amortized Cost | 3,032 | 29,011
Gross Unrealized Gains |  | 1
Gross Unrealized Losses |  | (7)
Fair Value | 3,032 | 29,005
Federal Government Sponsored Enterprise notes [Member] |  |
Available-for-sale securities: |  |
Amortized Cost |  | 3,992
Gross Unrealized Gains |  |
Gross Unrealized Losses |  | (14)
Fair Value |  | 3,978
International agency notes [Member] |  |
Available-for-sale securities: |  |
Amortized Cost |  | 291
Gross Unrealized Gains |  |
Gross Unrealized Losses |  |
Fair Value |  | 291
Mutual funds [Member] |  |
Available-for-sale securities: |  |
Amortized Cost |  | 5,353
Gross Unrealized Gains |  | 77
Gross Unrealized Losses |  |
Fair Value |  | 5,430
Corporate bonds [Member] |  |
Available-for-sale securities: |  |
Amortized Cost |  | 4,643
Gross Unrealized Gains |  |
Gross Unrealized Losses |  |
Fair Value |  | 4,643
Equity [Member] |  |
Available-for-sale securities: |  |
Amortized Cost | 393 | 74
Gross Unrealized Gains |  |
Gross Unrealized Losses | (33) | (26)
Fair Value | 360 | 48
U.S. Treasury notes [Member] |  |
Available-for-sale securities: |  |
Amortized Cost | 1,693 | 6,673
Gross Unrealized Gains |  |
Gross Unrealized Losses | (1) |
Fair Value | 1,692 | 6,673
Municipal bonds [Member] |  |
Available-for-sale securities: |  |
Amortized Cost | 888 | 8,201
Gross Unrealized Gains |  | 4
Gross Unrealized Losses |  | (1)
Fair Value | $ 888 | $ 8,204

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