Exit and disposal activities - Narrative (Details) $ in Millions				3 Months Ended
	Oct. 12, 2021 USD ($) store	Oct. 11, 2021 store	Dec. 20, 2018 USD ($)	May 31, 2022 USD ($)	Feb. 28, 2022 USD ($)	Aug. 31, 2021 USD ($)	May 31, 2021 USD ($)	Feb. 28, 2021 USD ($)	Aug. 31, 2020 USD ($)	Sep. 01, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings				$ (30,382)	$ (30,867)	$ (23,822)	$ (22,596)	$ (21,625)	$ (21,136)
Adoption of New Accounting Standards
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings									6
Retained Earnings
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings				(38,632)	$ (38,757)	$ (35,121)	$ (34,908)	$ (34,116)	(34,210)
Retained Earnings | Adoption of New Accounting Standards
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings									$ 3
Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred				1,700
Transformational Cost Management Program | United Kingdom
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	150	200
Transformational Cost Management Program | United States
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	150	250
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				467
Asset Impairments | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred				357
Employee Severance and Business Transition Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred				679
Information Technology Transformation and Other Exit Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred				183
Minimum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan	$ 3,300		$ 2,000	3,500
Expected cost				3,600
Minimum | Exit and Disposal Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected cost				3,300
Maximum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected cost				3,900
Maximum | Exit and Disposal Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected cost				$ 3,600