Goodwill and other intangible assets - Schedule of Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Feb. 28, 2022	Aug. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	$ 6,829	$ 4,421
Accumulated amortization	1,787	1,826
Total amortizable intangible assets, net	5,042	2,595
Indefinite-lived intangible assets	7,310	7,342
Total intangible assets, net	12,352	9,936
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	5,265	5,276
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	2,045	2,066
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	4,439	3,522
Accumulated amortization	1,457	1,335
Primary care provider network
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	1,244	0
Accumulated amortization	26	0
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	703	361
Accumulated amortization	242	226
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	352	156
Accumulated amortization	29	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	77	65
Accumulated amortization	$ 31	$ 29