Income Taxes - Reconciliation of effective tax rate (Details)	12 Months Ended
Jul. 31, 2020	Jul. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory rate	(21.00%)	(21.00%)
Increase (decrease) in income taxes resulting from:
Change in fair value of purchase consideration	3.20%	(40.20%)
Expiration of net operating loss carryforward	0.00%	9.90%
Impairment of long-lived assets	3.30%	0.00%
Other	0.70%	2.40%
Change in valuation allowance	13.80%	48.90%
Effective tax rate	0.00%	0.00%

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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