Exit and disposal activities - Restructuring Costs (Details) - Transformational Cost Management Program - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2021	May 31, 2020
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	$ 44	$ 290	$ 279	$ 455
Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	2	253	172	348
Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	27	27	63	76
Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	14	11	44	31
Lease obligations and other real estate costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	21	173	62	184
Lease obligations and other real estate costs | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	15	170	56	179
Lease obligations and other real estate costs | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	6	3	6	5
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	0	0
Asset impairments
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	14	29	19	44
Asset impairments | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	5	19	9	31
Asset impairments | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	9	10	10	13
Asset impairments | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	0	0	0
Employee severance and business transition costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	(2)	56	172	162
Employee severance and business transition costs | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	(19)	47	92	111
Employee severance and business transition costs | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	2	(2)	36	33
Employee severance and business transition costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	14	11	44	18
Information technology transformation and other exit costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	11	33	26	65
Information technology transformation and other exit costs | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	1	17	14	27
Information technology transformation and other exit costs | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	10	16	11	26
Information technology transformation and other exit costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges		$ 0	$ 1	$ 12