Exit and disposal activities - narrative (Details) $ in Millions			12 Months Ended
	Oct. 12, 2021 USD ($) store	Dec. 20, 2018 USD ($)	Aug. 31, 2022 USD ($) store	Aug. 31, 2021 USD ($)	Aug. 31, 2020 USD ($)	Sep. 01, 2019 USD ($)	Aug. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings			$ (29,366)	$ (23,822)	$ (21,136)		$ (24,152)
Adoption of new accounting standards
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings					6		442
Retained earnings
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings			(37,801)	(35,121)	(34,210)		(35,815)
Retained earnings | Adoption of new accounting standards
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings					3		$ 442
Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Costs incurred			2,000
Restructuring costs			$ 690	335	665
Transformational cost management program | United Kingdom
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	350
Number of stores closed | store			235
Transformational cost management program | United States
Restructuring Cost and Reserve [Line Items]
Number of stores closed | store			287
Transformational cost management program | Retained earnings | Adoption of new accounting standards
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings						$ 508
Lease obligations and other real estate costs | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Costs incurred			$ 603
Restructuring costs			249	108	215
Asset impairments | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Costs incurred			443
Restructuring costs			190	24	72
Employee severance and business transition costs | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Costs incurred			723
Restructuring costs			210	165	270
Information technology transformation and other exit costs | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Costs incurred			203
Restructuring costs			40	$ 38	$ 108
Minimum | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan	$ 3,300	$ 2,000
Expected restructuring costs			3,600
Minimum | Transformational cost management program | United States
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	450
Minimum | Exit and disposal costs | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs			3,300
Maximum | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan			3,500
Expected restructuring costs			3,900
Maximum | Transformational cost management program | United States
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	500
Maximum | Exit and disposal costs | Transformational cost management program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs			$ 3,600