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Debt Securities (Details) - USD ($) $ in Thousands | Apr. 30, 2019 | Jul. 31, 2018
--- | --- | ---
Available-for-sale securities: |  |  |
Amortized Cost |  | $ 301 | $ 5,613
Gross Unrealized Gains |  |  |
Gross Unrealized Losses |  |  | (1)
Fair Value |  | 301 | 5,612
Certificates of deposit [Member] |  |  |
Available-for-sale securities: |  |  |
Amortized Cost | [1] |  | 3,032
Gross Unrealized Gains | [1] |  |
Gross Unrealized Losses | [1] |  |
Fair Value | [1] |  | 3,032
U.S. Treasury notes [Member] |  |  |
Available-for-sale securities: |  |  |
Amortized Cost |  |  | 1,693
Gross Unrealized Gains |  |  |
Gross Unrealized Losses |  |  | (1)
Fair Value |  |  | 1,692
Municipal bonds [Member] |  |  |
Available-for-sale securities: |  |  |
Amortized Cost |  | 301 | 888
Gross Unrealized Gains |  |  |
Gross Unrealized Losses |  |  |
Fair Value |  | $ 301 | $ 888
[1] | Each of the Company's certificates of deposit had a CUSIP, was purchased in the secondary market through a broker, and may be sold in the secondary market.

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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