Marketable Securities (Schedule of investment income) (Details) - USD ($)	3 Months Ended
Oct. 31, 2019	Oct. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Gain on sale of marketable securities	$ 46,981
Interest income	10,278	13,561
Dividend income	7,744	8,874
Total	$ 65,003	$ 22,435

Amount of dividend income on nonoperating securities.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

+ Details

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(a),(b))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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- References

No definition available.

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Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

+ References

No definition available.

+ Details

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