Exit and disposal activities - Narrative and Changes in Restructuring Liabilities (Details) $ in Millions			3 Months Ended	6 Months Ended	16 Months Ended
	Apr. 02, 2019 store	Oct. 24, 2017 store	Feb. 28, 2019 USD ($)	Feb. 28, 2019 USD ($)	Feb. 28, 2019 USD ($)
Transformational Cost Management Program
Restructuring Reserve Disclosures [Abstract]
Restructuring costs			$ 150	$ 179
Restructuring Reserve [Roll Forward]
Beginning Balance				0
Costs				179
Payments				(33)
Other - non cash				(117)
Ending Balance			30	30	$ 30
Transformational Cost Management Program | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Restructuring costs			39	62
Restructuring Reserve [Roll Forward]
Beginning Balance				0
Costs				62
Payments				(33)
Other - non cash				0
Ending Balance			30	30	30
Transformational Cost Management Program | Asset impairments
Restructuring Reserve Disclosures [Abstract]
Restructuring costs			111	117
Restructuring Reserve [Roll Forward]
Beginning Balance				0
Costs				117
Payments				0
Other - non cash				(117)
Ending Balance			0	0	0
Store Optimization Program
Restructuring Reserve Disclosures [Abstract]
Number of stores expected to close | store		600
Expected cost			350	350	350
Restructuring costs			31	51	150
Restructuring Reserve [Roll Forward]
Beginning Balance				329
Costs				51
Payments				(147)
Other - non cash				103
Ending Balance			336	336	336
Store Optimization Program | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Expected cost			190	190	190
Restructuring costs			22	49	130
Restructuring Reserve [Roll Forward]
Beginning Balance				21
Costs				49
Payments				(56)
Other - non cash				0
Ending Balance			14	14	14
Store Optimization Program | Lease obligations and other real estate costs
Restructuring Reserve Disclosures [Abstract]
Expected cost			160	160	160
Restructuring costs			9	2	21
Restructuring Reserve [Roll Forward]
Beginning Balance				308
Costs				2
Payments				(91)
Other - non cash				103
Ending Balance			321	321	321
Cost Transformation Program
Restructuring Reserve [Roll Forward]
Beginning Balance				421
Payments				(46)
Other - non cash				19
Ending Balance			395	395	395
Cost Transformation Program | Severance and other business transition and exit costs
Restructuring Reserve [Roll Forward]
Beginning Balance				7
Payments				(2)
Other - non cash				0
Ending Balance			5	5	5
Cost Transformation Program | Real estate costs
Restructuring Reserve [Roll Forward]
Beginning Balance				414
Payments				(44)
Other - non cash				19
Ending Balance			$ 390	$ 390	$ 390
Subsequent Event | Store Optimization Program
Restructuring Reserve Disclosures [Abstract]
Number of stores expected to close | store	750