Exit and disposal activities - Restructuring Costs (Details) - Transformational Cost Management Program - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	$ 154	$ 105	$ 235	$ 164
Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	122	47	170	95
Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	16	40	36	50
Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	17	18	29	20
Lease obligations and other real estate costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	18	10	40	13
Lease obligations and other real estate costs | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	18	9	40	10
Lease obligations and other real estate costs | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	0	1	0	3
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	4	3	5	14
Asset impairments | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	1	3	5	11
Asset impairments | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	3	0	0	3
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	122	71	174	106
Employee severance and business transition costs | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	99	34	111	65
Employee severance and business transition costs | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	6	32	34	34
Employee severance and business transition costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	17	6	29	7
Information technology transformation and other exit costs
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	11	21	15	31
Information technology transformation and other exit costs | Reportable Segments | United States
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	4	1	14	9
Information technology transformation and other exit costs | Reportable Segments | International
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	7	7	2	10
Information technology transformation and other exit costs | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Total pre-tax exit and disposal charges	$ 0	$ 13	$ 0	$ 13