Summary of major accounting policies - property plant and equipment (Details) - USD ($) $ in Millions	Aug. 31, 2023	Aug. 31, 2022
Property, Plant and Equipment [Line Items]
Property, plant, and equipment and finance lease right-of-use asset, before accumulated depreciation and amortization	$ 24,540	$ 24,572
Property, plant, and equipment and finance lease right-of-use asset, accumulated depreciation and amortization	12,953	12,843
Property and equipment, net	$ 11,587	11,729
Land and land improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Property and equipment	$ 1,778	2,333
Buildings and building improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 6,683	6,996
Buildings and building improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Buildings and building improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	50 years
Fixtures and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 9,782	9,375
Fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Capitalized system development costs and software
Property, Plant and Equipment [Line Items]
Property and equipment	$ 3,821	3,087
Capitalized system development costs and software | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Capitalized system development costs and software | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Asset under construction
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,400	1,785
Finance lease properties
Property, Plant and Equipment [Line Items]
Finance lease properties	$ 1,075	$ 996