Exit and disposal activities - narrative (Details) $ in Millions				12 Months Ended		22 Months Ended
	Oct. 28, 2019 USD ($) store	Dec. 20, 2018 USD ($)	Oct. 24, 2017 store	Aug. 31, 2019 USD ($) store	Aug. 31, 2018 USD ($)	Aug. 31, 2019 USD ($)
Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Number of store expected to close | store				200
Restructuring costs				$ 432
Store Optimization Program
Restructuring Cost and Reserve [Line Items]
Number of store expected to close | store			600
Expected restructuring costs				350		$ 350
Restructuring costs				196	$ 100	296
Lease obligations and other real estate costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Restructuring costs				25
Lease obligations and other real estate costs | Store Optimization Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs				160		160
Restructuring costs				119	19	138
Asset impairments | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Restructuring costs				260
Employee severance and other exit costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Restructuring costs				125
Employee severance and other exit costs | Store Optimization Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs				190		190
Restructuring costs				77	$ 81	158
Maximum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs				2,400		2,400
Maximum | Exit And Disposal Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs				2,000		2,000
Minimum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan		$ 1,500
Expected restructuring costs				1,900		1,900
Minimum | Exit And Disposal Costs | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring costs				$ 1,600		$ 1,600
Subsequent Event | Store Optimization Program
Restructuring Cost and Reserve [Line Items]
Number of store expected to close | store	750
Forecast | Maximum | Transformational Cost Management Program
Restructuring Cost and Reserve [Line Items]
Expected annual cost savings of restructuring plan	$ 1,800