Goodwill and other intangible assets - schedule of finite-lived intangible assets by major class (Details) - USD ($) $ in Millions	Aug. 31, 2021	Aug. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Total gross amortizable intangible assets	$ 4,421	$ 4,247
Total accumulated amortization	1,826	1,406
Total amortizable intangible assets, net	2,595	2,841
Total indefinite-lived intangible assets	7,342	7,231
Total intangible assets, net	9,936	10,072
Tradenames and trademarks
Finite-Lived Intangible Assets [Line Items]
Total indefinite-lived intangible assets	5,276	5,203
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Total indefinite-lived intangible assets	2,066	2,028
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Total gross amortizable intangible assets	3,522	3,502
Total accumulated amortization	1,335	1,089
Tradenames and trademarks
Finite-Lived Intangible Assets [Line Items]
Total gross amortizable intangible assets	361	348
Total accumulated amortization	226	196
Purchasing and payer contracts
Finite-Lived Intangible Assets [Line Items]
Total gross amortizable intangible assets	317	337
Total accumulated amortization	227	95
Others
Finite-Lived Intangible Assets [Line Items]
Total gross amortizable intangible assets	221	60
Total accumulated amortization	$ 37	$ 26