Exit and disposal activities - restructuring costs (Details) - Transformational cost management program - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	$ 335	$ 665	$ 282
Reportable Segments | United States
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	217	444	147
Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	72	163	134
Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	46	58	1
Lease obligations and other real estate costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	108	215	30
Lease obligations and other real estate costs | Reportable Segments | United States
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	103	191	5
Lease obligations and other real estate costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	6	9	26
Lease obligations and other real estate costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	0	14	0
Asset impairments
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	24	72	156
Asset impairments | Reportable Segments | United States
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	15	51	95
Asset impairments | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	9	19	61
Asset impairments | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	0	2	0
Employee severance and business transition costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	165	270	78
Employee severance and business transition costs | Reportable Segments | United States
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	79	132	41
Employee severance and business transition costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	40	93	37
Employee severance and business transition costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	45	45	1
Information technology transformation and other exit costs
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	38	108	17
Information technology transformation and other exit costs | Reportable Segments | United States
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	20	70	6
Information technology transformation and other exit costs | Reportable Segments | International
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	17	42	10
Information technology transformation and other exit costs | Corporate and Other
Restructuring Reserve Disclosures [Abstract]
Total pre-tax exit and disposal charges	$ 0	$ (4)	$ 0