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, 2023 USD ($) market store clinic	Aug. 31, 2023 USD ($)	Aug. 31, 2022 USD ($)	Nov. 30, 2022 USD ($)	Sep. 01, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings			$ (27,588)	$ (28,322)	$ (29,366)	$ (24,582)
Retained Earnings
Restructuring Cost and Reserve [Line Items]
Cumulative effect adjustment to decrease retained earnings			(32,573)	(33,058)	(37,801)	$ (33,664)
Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			$ 3,200
Number of markets exited | market			6
Number of clinics closed | clinic			70
Transformational Cost Management Program | United Kingdom
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	650
Number of stores closed | store			364
Transformational Cost Management Program | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Number of stores closed | store			563
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
Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Impairment			$ 124
Lease Obligations and Other Real Estate Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			1,200
Asset Impairments | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			894
Employee Severance and Business Transition Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			900
Information Technology Transformation and Other Exit Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Costs incurred			$ 257
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				4,100
Minimum | Transformational Cost Management Program | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	650
Minimum | Exit and Disposal Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected cost				3,800
Minimum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan				3,500
Maximum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected cost				4,400
Maximum | Transformational Cost Management Program | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Number of stores expected to close | store	700
Maximum | Exit and Disposal Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected cost				4,100
Maximum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan				$ 4,500	$ 3,500