Property and Equipment - Schedule of property and equipment (Details) - USD ($) $ in Millions	12 Months Ended
Jul. 31, 2020	Jul. 31, 2019
Property, Plant and Equipment [Line Items]
Equipment	$ 226	$ 421
Computer software	870	860
Furniture and fixtures	93	90
Leasehold improvements	298	278
Land	79	79
Buildings	372	368
Capital in progress	90	65
Total property plant and equipment, gross	2,028	2,161
Less accumulated depreciation and amortization	(1,294)	(1,381)
Total property and equipment, net	$ 734	$ 780
Minimum
Property, Plant and Equipment [Line Items]
Life in years	2 years
Maximum
Property, Plant and Equipment [Line Items]
Life in years	30 years
Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Life in years	3 years
Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Life in years	5 years
Computer software \| Minimum
Property, Plant and Equipment [Line Items]
Life in years	2 years
Computer software \| Maximum
Property, Plant and Equipment [Line Items]
Life in years	6 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Life in years	5 years
Leasehold improvements \| Minimum
Property, Plant and Equipment [Line Items]
Life in years	2 years
Leasehold improvements \| Maximum
Property, Plant and Equipment [Line Items]
Life in years	16 years
Buildings \| Minimum
Property, Plant and Equipment [Line Items]
Life in years	5 years
Buildings \| Maximum
Property, Plant and Equipment [Line Items]
Life in years	30 years

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation of building structures held for productive use including addition, improvement, or renovation to the structure, including, but not limited to, interior masonry, interior flooring, electrical, and plumbing.

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Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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Amount before accumulated depreciation of equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.

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Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

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Amount before accumulated depreciation of tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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