Summary of major accounting policies - property plant and equipment (Details) - USD ($) $ in Millions	Aug. 31, 2024	Aug. 31, 2023
Property, Plant and Equipment [Line Items]
Finance lease properties	$ 1,143	$ 1,075
Property, plant, and equipment and finance lease right-of-use asset, before accumulated depreciation and amortization	22,636	24,540
Property, plant, and equipment and finance lease right-of-use asset, accumulated depreciation and amortization	12,863	12,953
Property and equipment, net	$ 9,772	11,587
Land and land improvements 1
Property, Plant and Equipment [Line Items]
Estimated useful life	20 years
Property and equipment	$ 1,455	1,778
Buildings and building improvements
Property, Plant and Equipment [Line Items]
Property and equipment	$ 6,117	6,683
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	$ 9,720	9,782
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	$ 3,528	3,821
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	$ 673	$ 1,400