Goodwill and other intangible assets - Schedule of Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Nov. 30, 2021	Aug. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	$ 7,479	$ 4,421
Accumulated amortization	1,953	1,826
Total amortizable intangible assets, net	5,526	2,595
Indefinite-lived intangible assets	7,244	7,342
Total intangible assets, net	12,770	9,936
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	5,208	5,276
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	2,036	2,066
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	4,430	3,522
Accumulated amortization	1,395	1,335
Primary care provider network
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	1,660	0
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	708	361
Accumulated amortization	228	226
Purchasing and payer contracts
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	317	317
Accumulated amortization	284	227
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	290	0
Accumulated amortization	17	0
Others
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	75	221
Accumulated amortization	$ 29	$ 37