Exit and disposal activities - Restructuring Reserve Activity (Details) $ in Millions	6 Months Ended
	Feb. 29, 2020 USD ($)
Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance	$ 78
Costs	173
Payments	(70)
Other - non cash	(20)
ASC 842 Leases adoption	(4)
Currency translation adjustment	1
Ending balance	158
Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance	429
Costs	39
Payments	(50)
Other - non cash	(6)
ASC 842 Leases adoption	(378)
Ending balance	34
Lease obligations and other real estate costs | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance	17
Costs	11
Payments	(1)
Other - non cash	3
ASC 842 Leases adoption	(4)
Currency translation adjustment	1
Ending balance	27
Lease obligations and other real estate costs | Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance	407
Costs	21
Payments	(18)
Other - non cash	(1)
ASC 842 Leases adoption	(378)
Ending balance	31
Asset impairment | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance	0
Costs	15
Payments	0
Other - non cash	(15)
ASC 842 Leases adoption	0
Currency translation adjustment	0
Ending balance	0
Employee severance and business transition costs | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance	57
Costs	111
Payments	(59)
Other - non cash	0
ASC 842 Leases adoption	0
Currency translation adjustment	0
Ending balance	110
Information technology transformation and other exit costs | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance	4
Costs	36
Payments	(10)
Other - non cash	(8)
ASC 842 Leases adoption	0
Currency translation adjustment	0
Ending balance	22
Employee severance and other exit costs | Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance	22
Costs	18
Payments	(32)
Other - non cash	(5)
ASC 842 Leases adoption	0
Ending balance	$ 3