Exit and disposal activities - restructuring reserve activity (Details) - USD ($) $ in Millions	12 Months Ended		22 Months Ended
	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2019
Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance	$ 0
Restructuring costs	432
Payments	(90)
Other - non cash	(265)
Currency translation adjustments	1
Ending balance	78	$ 0	$ 78
Transformational Cost Management Program | Employee severance and other exit costs
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	125
Payments	(69)
Other - non cash	0
Currency translation adjustments	1
Ending balance	57	0	57
Transformational Cost Management Program | Asset impairments
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	260
Payments	0
Other - non cash	(260)
Currency translation adjustments	0
Ending balance	0	0	0
Transformational Cost Management Program | Lease obligations and other real estate costs
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	25
Payments	(8)
Other - non cash	0
Currency translation adjustments	0
Ending balance	17	0	17
Transformational Cost Management Program | Information technology transformation and other exit costs
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring costs	22
Payments	(13)
Other - non cash	(6)
Currency translation adjustments	0
Ending balance	4	0	4
Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance	329	0
Restructuring costs	196	100	296
Payments	(240)	(78)
Other - non cash	144	307
Ending balance	429	329	429
Store Optimization Program | Employee severance and other exit costs
Restructuring Reserve [Roll Forward]
Beginning balance	21	0
Restructuring costs	77	81	158
Payments	(69)	(60)
Other - non cash	(7)	0
Ending balance	22	21	22
Store Optimization Program | Lease obligations and other real estate costs
Restructuring Reserve [Roll Forward]
Beginning balance	308	0
Restructuring costs	119	19	138
Payments	(171)	(18)
Other - non cash	152	307
Ending balance	407	308	407
Cost Transformation Program
Restructuring Reserve [Roll Forward]
Beginning balance	421	600
Payments	(90)	(207)
Other - non cash	59	29
Currency translation adjustments		(1)
Ending balance	390	421	390
Cost Transformation Program | Employee severance and other exit costs
Restructuring Reserve [Roll Forward]
Beginning balance	7	79
Payments	(4)	(68)
Other - non cash	0	(3)
Currency translation adjustments		(1)
Ending balance	3	7	3
Cost Transformation Program | Real estate costs
Restructuring Reserve [Roll Forward]
Beginning balance	414	521
Payments	(86)	(139)
Other - non cash	59	32
Currency translation adjustments		0
Ending balance	$ 387	$ 414	$ 387