Sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 34,631	$ 34,591	$ 104,791	$ 102,912
Reportable Segments | Retail Pharmacy USA
Disaggregation of Revenue [Line Items]
Sales	27,357	26,513	80,734	78,491
Reportable Segments | Retail Pharmacy USA | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	20,478	19,585	60,084	57,624
Reportable Segments | Retail Pharmacy USA | Retail
Disaggregation of Revenue [Line Items]
Sales	6,878	6,928	20,650	20,867
Reportable Segments | Retail Pharmacy International
Disaggregation of Revenue [Line Items]
Sales	1,903	2,776	7,704	8,759
Reportable Segments | Retail Pharmacy International | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	927	1,047	2,954	3,096
Reportable Segments | Retail Pharmacy International | Retail
Disaggregation of Revenue [Line Items]
Sales	975	1,730	4,750	5,662
Reportable Segments | Pharmaceutical Wholesale
Disaggregation of Revenue [Line Items]
Sales	5,899	5,865	17,971	17,311
Eliminations
Disaggregation of Revenue [Line Items]
Sales	$ (527)	$ (563)	$ (1,618)	$ (1,649)