Exit and disposal activities (Details) $ in Millions		6 Months Ended
	Oct. 24, 2017 store	Feb. 28, 2018 USD ($)
Store Optimization Program
Restructuring Reserve Disclosures [Abstract]
Number of stores expected to close | store	600
Duration of restructuring plan	18 months
Expected cost		$ 450
Store Optimization Program | Lease obligations and other real estate costs
Restructuring Reserve Disclosures [Abstract]
Expected cost		270
Store Optimization Program | Severance and other business transition and exit costs
Restructuring Reserve Disclosures [Abstract]
Expected cost		180
Cost Transformation Program
Restructuring Reserve [Roll Forward]
Beginning Balance		600
Payments		(142)
Other - non cash		9
Ending Balance		467
Cost Transformation Program | Real estate costs
Restructuring Reserve [Roll Forward]
Beginning Balance		521
Payments		(79)
Other - non cash		9
Ending Balance		451
Cost Transformation Program | Severance and other business transition and exit costs
Restructuring Reserve [Roll Forward]
Beginning Balance		79
Payments		(63)
Other - non cash		0
Ending Balance		$ 16