Goodwill and other intangible assets - Schedule of Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	May 31, 2022	Aug. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	$ 6,741	$ 4,421
Accumulated amortization	1,853	1,826
Total amortizable intangible assets, net	4,888	2,595
Indefinite-lived intangible assets	6,695	7,342
Total intangible assets, net	11,583	9,936
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	4,835	5,276
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	1,860	2,066
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	4,364	3,522
Accumulated amortization	1,487	1,335
Primary care provider network
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	1,244	0
Accumulated amortization	43	0
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	685	361
Accumulated amortization	244	226
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	355	156
Accumulated amortization	43	8
Purchasing and payor contracts
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	15	317
Accumulated amortization	3	227
Others
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	78	65
Accumulated amortization	$ 33	$ 29