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Goodwill and other intangible assets - narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021	Jun. 01, 2023	May 31, 2023
Goodwill [Line Items]
Goodwill	$ 28,187	$ 22,280	$ 12,421
Indefinite lived intangible assets	5,477	5,528
Impairment of definite-lived intangible assets	0	0	0
Amortization expense for intangible assets	$ 815	$ 639	523
Minimum
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount	3.00%	3.00%		3.00%	3.00%
Maximum
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount	7.00%	7.00%		227.00%	32.00%
Pharmacy licenses
Goodwill [Line Items]
Indefinite lived intangible assets	$ 828	$ 1,209
Boots Reporting Unit
Goodwill [Line Items]
Goodwill	977	906
Impairment of intangible assets	431	783	$ 49
Indefinite lived intangible assets	$ 5,500	$ 5,500