Exit and disposal activities - Narrative (Details) $ in Millions			3 Months Ended	12 Months Ended
	Oct. 12, 2021 USD ($) store	Dec. 20, 2018 USD ($)	Nov. 30, 2022 USD ($) store	Aug. 31, 2022 USD ($)	Aug. 31, 2021 USD ($)	Nov. 30, 2021 USD ($)	Sep. 01, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings			$ (24,582)	$ (29,366)	$ (23,822)	$ (30,579)
Retained Earnings
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings			(33,664)	(37,801)	(35,121)	$ (38,286)
Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			$ 2,100
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			244
Transformational Cost Management Program | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Number of stores closed | store			363
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			$ 681
Asset Impairments | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			461
Employee Severance and Business Transition Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			739
Information Technology Transformation and Other Exit Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			219
Minimum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan	$ 3,300	$ 2,000			$ 3,300
Expected cost			3,600
Minimum | Transformational Cost Management Program | U.S. Retail Pharmacy
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 cost			3,300
Maximum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan				$ 3,500
Expected cost			3,900
Maximum | Transformational Cost Management Program | U.S. Retail Pharmacy
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 cost			$ 3,600