Exit and disposal activities - Narrative and Changes in Restructuring Liabilities (Details) $ in Millions			3 Months Ended	9 Months Ended	19 Months Ended
	Jun. 27, 2019 store	Oct. 24, 2017 store	May 31, 2019 USD ($)	May 31, 2019 USD ($)	May 31, 2019 USD ($)
Transformational cost management program
Restructuring Reserve [Roll Forward]
Beginning Balance				$ 0
Costs				235
Payments				(57)
Other - non cash				(149)
Ending Balance			$ 28	28	$ 28
Restructuring costs			56	235
Transformational cost management program | Severance and other business transition and exit costs
Restructuring Reserve [Roll Forward]
Beginning Balance				0
Costs				86
Payments				(57)
Other - non cash				0
Ending Balance			28	28	28
Restructuring costs			24	86
Transformational cost management program | Asset impairments
Restructuring Reserve [Roll Forward]
Beginning Balance				0
Costs				149
Payments				0
Other - non cash				(149)
Ending Balance			0	0	0
Restructuring costs			32	149
Store optimization program
Restructuring Reserve [Roll Forward]
Beginning Balance				329
Costs				99
Payments				(194)
Other - non cash				104
Ending Balance			338	338	338
Number of stores expected to close | store		600
Expected cost			350	350	350
Restructuring costs			49	99	200
Store optimization program | Severance and other business transition and exit costs
Restructuring Reserve [Roll Forward]
Beginning Balance				21
Costs				54
Payments				(69)
Other - non cash				0
Ending Balance			6	6	6
Expected cost			190	190	190
Restructuring costs			5	54	136
Store optimization program | Lease obligations and other real estate costs
Restructuring Reserve [Roll Forward]
Beginning Balance				308
Costs				45
Payments				(125)
Other - non cash				104
Ending Balance			332	332	332
Expected cost			160	160	160
Restructuring costs			44	45	64
Cost Transformation Program
Restructuring Reserve [Roll Forward]
Beginning Balance				421
Payments				(70)
Other - non cash				51
Ending Balance			403	403	403
Cost Transformation Program | Severance and other business transition and exit costs
Restructuring Reserve [Roll Forward]
Beginning Balance				7
Payments				(3)
Other - non cash				0
Ending Balance			4	4	4
Cost Transformation Program | Real estate costs
Restructuring Reserve [Roll Forward]
Beginning Balance				414
Payments				(67)
Other - non cash				51
Ending Balance			$ 399	$ 399	$ 399
Subsequent event | Store optimization program
Restructuring Reserve [Roll Forward]
Number of stores expected to close | store	750