Exit and disposal activities - Restructuring Reserve Activity (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	May 31, 2020	May 31, 2020
Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance		$ 78
Costs		467
Payments		(151)
Other		(205)
ASC 842 Leases adoption		(4)
Currency		0
Ending balance	$ 186	186
Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance		429
Costs		49
Payments		(67)
Other		(21)
ASC 842 Leases adoption		(378)
Ending balance	12	12
Lease obligations and other real estate costs | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance		17
Costs		184
Payments		(27)
Other	153	153
ASC 842 Leases adoption		(4)
Currency		0
Ending balance	17	17
Lease obligations and other real estate costs | Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance		407
Costs		24
Payments		(32)
Other		(13)
ASC 842 Leases adoption		(378)
Ending balance	8	8
Asset impairments | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance		0
Costs		45
Payments		0
Other		(45)
ASC 842 Leases adoption		0
Currency		0
Ending balance	0	0
Employee severance and business transition costs | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance		57
Costs		168
Payments		(92)
Other		7
ASC 842 Leases adoption		0
Currency		0
Ending balance	140	140
Information technology transformation and other exit costs | Transformational Cost Management Program
Restructuring Reserve [Roll Forward]
Beginning balance		4
Costs		70
Payments		(31)
Other		(13)
ASC 842 Leases adoption		0
Currency		0
Ending balance	29	29
Employee severance and other exit costs | Store Optimization Program
Restructuring Reserve [Roll Forward]
Beginning balance		22
Costs		25
Payments		(34)
Other		(8)
ASC 842 Leases adoption		0
Ending balance	$ 4	$ 4