Goodwill and other intangible assets - Schedule of Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Feb. 28, 2021	Aug. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	$ 4,333	$ 4,247
Accumulated amortization	1,601	1,406
Total amortizable intangible assets, net	2,732	2,841
Indefinite-lived intangible assets	7,753	7,231
Total intangible assets, net	10,486	10,072
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	5,626	5,203
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	2,127	2,028
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	3,570	3,502
Accumulated amortization	1,234	1,089
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	364	348
Accumulated amortization	215	196
Purchasing and payer contracts
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	337	337
Accumulated amortization	125	95
Non-compete agreements and others
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	62	60
Accumulated amortization	$ 27	$ 26