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Goodwill and other intangible assets - narrative (Details) $ in Millions	12 Months Ended
	Aug. 31, 2021 USD ($)	Aug. 31, 2020 USD ($) reporting_unit	Aug. 31, 2019 USD ($)	Jun. 01, 2021	Jun. 01, 2020
Goodwill [Line Items]
Goodwill	$ 12,421	$ 12,013	$ 13,542
Indefinite lived intangible assets	7,342	$ 7,231
Number of reporting segments included in impairment analysis \| reporting_unit		2
Goodwill impairment loss		$ 1,675
Impairment of definite-lived intangible assets	0	47
Amortization expense for intangible assets	523	384	473
Minimum
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount				18.00%
Maximum
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount				195.00%
Pharmacy licenses
Goodwill [Line Items]
Indefinite lived intangible assets	2,066	2,028
Other International Reporting Unit
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount				29.00%	4.00%
Goodwill	400
Boots Reporting Unit
Goodwill [Line Items]
Goodwill	1,100
Impairment of intangible assets	49	300
Indefinite lived intangible assets	$ 7,300	7,200
Goodwill impairment loss		$ 1,700
Boots Reporting Unit \| Trade names \| Minimum
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount	5.00%
Boots Reporting Unit \| Trade names \| Maximum
Goodwill [Line Items]
Percentage of reporting unit fair value in excess of carrying amount	27.00%
Boots Reporting Unit \| Pharmacy licenses
Goodwill [Line Items]
Impairment of intangible assets			$ 73