Exit and disposal activities - restructuring costs (Details) - Transformational cost management program - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2024	Aug. 31, 2023	Aug. 31, 2022
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	$ 835	$ 1,158	$ 690
Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	770	816	546
Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	32	213	118
Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	26	115	0
Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	6	14	25
Lease obligations and other real estate costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	535	516	249
Lease obligations and other real estate costs | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	535	492	247
Lease obligations and other real estate costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	0	23	2
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	0	1	0
Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	128	441	190
Asset impairments | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	104	183	132
Asset impairments | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	16	149	58
Asset impairments | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	8	109	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	102	150	210
Employee severance and business transition costs | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	93	111	156
Employee severance and business transition costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	(3)	20	29
Employee severance and business transition costs | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	6	6	0
Employee severance and business transition costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	6	13	25
Information technology transformation and other exit costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	70	51	40
Information technology transformation and other exit costs | Reportable Segments | U.S. Retail Pharmacy
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	39	30	12
Information technology transformation and other exit costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	19	21	29
Information technology transformation and other exit costs | Reportable Segments | U.S. Healthcare
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	13	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