Goodwill and other intangible assets - Schedule of Finite-Lived Intangible Assets by Major Class (Details) - USD ($) $ in Millions	Nov. 30, 2020	Aug. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	$ 5,226	$ 5,197
Accumulated amortization	1,972	1,860
Total amortizable intangible assets, net	3,254	3,337
Indefinite-lived intangible assets	7,452	7,416
Total intangible assets, net	10,706	10,753
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	5,410	5,388
Pharmacy licenses
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	2,042	2,028
Customer relationships and loyalty card holders
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	4,409	4,389
Accumulated amortization	1,603	1,511
Trade names and trademarks
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	419	410
Accumulated amortization	242	228
Purchasing and payer contracts
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	337	337
Accumulated amortization	101	95
Non-compete agreements and others
Finite-Lived Intangible Assets [Line Items]
Gross amortizable intangible assets	61	61
Accumulated amortization	$ 26	$ 26