Exit and disposal activities - restructuring reserve activity (Details) $ in Millions	12 Months Ended
	Aug. 31, 2018 USD ($)
Store Optimization Program
Restructuring Reserve [Roll Forward]
August 31, 2017	$ 0
Restructuring costs	100
Payments	(78)
Other - non cash	307
August 31, 2018	329
Store Optimization Program | Lease obligations and other real estate costs
Restructuring Reserve [Roll Forward]
August 31, 2017	0
Restructuring costs	19
Payments	(18)
Other - non cash	307
August 31, 2018	308
Store Optimization Program | Employee severance and other exit costs
Restructuring Reserve [Roll Forward]
August 31, 2017	0
Restructuring costs	81
Payments	(60)
Other - non cash	0
August 31, 2018	21
Cost Transformation Program
Restructuring Reserve [Roll Forward]
August 31, 2017	600
Payments	(207)
Other - non cash	29
Currency translation adjustments	(1)
August 31, 2018	421
Cost Transformation Program | Employee severance and other exit costs
Restructuring Reserve [Roll Forward]
August 31, 2017	79
Payments	(68)
Other - non cash	(3)
Currency translation adjustments	(1)
August 31, 2018	7
Cost Transformation Program | Real estate costs
Restructuring Reserve [Roll Forward]
August 31, 2017	521
Payments	(139)
Other - non cash	32
Currency translation adjustments	0
August 31, 2018	$ 414