Goodwill and other intangible assets - Schedule of Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	May 31, 2021	Aug. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	$ 4,510	$ 4,247
Accumulated amortization	1,749	1,406
Total amortizable intangible assets, net	2,761	2,841
Indefinite-lived intangible assets	7,675	7,231
Total intangible assets, net	10,435	10,072
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	5,526	5,203
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	2,148	2,028
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	3,581	3,502
Accumulated amortization	1,306	1,089
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	373	348
Accumulated amortization	226	196
Purchasing and payer contracts
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	337	337
Accumulated amortization	185	95
Others
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	218	60
Accumulated amortization	$ 32	$ 26