Exit and disposal activities - Restructuring Costs (Details) - Transformational Cost Management Program - USD ($) $ in Millions	3 Months Ended
	Nov. 30, 2023	Nov. 30, 2022
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	$ 77	$ 130
Reportable segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	64	119
Reportable segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	6	6
Reportable segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	2	0
Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	4	4
Lease obligations and other real estate costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	36	79
Lease obligations and other real estate costs | Reportable segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	36	79
Lease obligations and other real estate costs | Reportable segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0
Lease obligations and other real estate costs | Reportable segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0
Lease obligations and other real estate costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0
Asset impairments
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	10	18
Asset impairments | Reportable segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	3	18
Asset impairments | Reportable segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	7	0
Asset impairments | Reportable segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0
Asset impairments | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0
Employee severance and business transition costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	27	16
Employee severance and business transition costs | Reportable segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	22	11
Employee severance and business transition costs | Reportable segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	(1)	1
Employee severance and business transition costs | Reportable segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	2	0
Employee severance and business transition costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	4	4
Information technology transformation and other exit costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	4	17
Information technology transformation and other exit costs | Reportable segments | U.S. Retail Pharmacy
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	3	11
Information technology transformation and other exit costs | Reportable segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	5
Information technology transformation and other exit costs | Reportable segments | U.S. Healthcare
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0
Information technology transformation and other exit costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	$ 0	$ 0