Exit and disposal activities - restructuring costs (Details) - Transformational cost management program - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	$ 1,158	$ 690	$ 335
Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	816	546	217
Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	213	118	72
Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	115	0	0
Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	14	25	46
Lease obligations and other real estate costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	516	249	108
Lease obligations and other real estate costs | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	492	247	103
Lease obligations and other real estate costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	23	2	6
Lease obligations and other real estate costs | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	0	0	0
Lease obligations and other real estate costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	1	0	0
Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	441	190	24
Asset impairments | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	183	132	15
Asset impairments | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	149	58	9
Asset impairments | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	109	0	0
Asset impairments | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	0	0	0
Employee severance and business transition costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	150	210	165
Employee severance and business transition costs | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	111	156	79
Employee severance and business transition costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	20	29	40
Employee severance and business transition costs | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	6	0	0
Employee severance and business transition costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	13	25	45
Information technology transformation and other exit costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	51	40	38
Information technology transformation and other exit costs | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	30	12	20
Information technology transformation and other exit costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	21	29	17
Information technology transformation and other exit costs | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	0	0	0
Information technology transformation and other exit costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	$ 0	$ 0	$ 0