Exit and disposal activities (Details) $ in Millions		3 Months Ended
	Oct. 24, 2017 USD ($) store	Nov. 30, 2017 USD ($)
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		(81)
Ending Balance		519
Cost Transformation Program | Real estate costs
Restructuring Reserve [Roll Forward]
Beginning Balance		521
Payments		(42)
Ending Balance		479
Cost Transformation Program | Severance and other business transition and exit costs
Restructuring Reserve [Roll Forward]
Beginning Balance		79
Payments		(39)
Ending Balance		$ 40