Summary of major accounting policies - property plant and equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2022	Aug. 31, 2021
Property, Plant and Equipment [Line Items]
Property, plant, and equipment and finance lease right-of-use asset, before accumulated depreciation and amortization	$ 24,572	$ 25,321
Property, plant, and equipment and finance lease right-of-use asset, accumulated depreciation and amortization	12,843	13,073
Property and equipment, net	$ 11,729	12,247
Land and land improvements
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Property and equipment	$ 2,333	2,782
Buildings and building improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 6,996	7,453
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	$ 9,375	9,974
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	$ 3,087	2,802
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	$ 1,785	1,294
Finance lease properties
Property, Plant and Equipment [Line Items]
Finance lease properties	$ 996	$ 1,016