Income Taxes - Reconciliation of effective tax rate (Details)	12 Months Ended
Jul. 31, 2019	Jul. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory rate	(21.00%)	(26.50%)
Increase (decrease) in income taxes resulting from:
Change in fair value of purchase consideration	(40.20%)	28.50%
Expiration of net operating loss carryforward	9.90%	0.00%
Other	2.40%	0.90%
Tax rate change	0.00%	(88.70%)
Change in valuation allowance	48.90%	85.80%
Effective tax rate	0.00%	0.00%

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration