Sales (Details) - USD ($) $ in Millions	3 Months Ended
	Nov. 30, 2019	Nov. 30, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 34,339	$ 33,793
Reportable Segments | Retail Pharmacy USA
Disaggregation of Revenue [Line Items]
Sales	26,133	25,721
Reportable Segments | Retail Pharmacy USA | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	19,705	19,147
Reportable Segments | Retail Pharmacy USA | Retail
Disaggregation of Revenue [Line Items]
Sales	6,428	6,574
Reportable Segments | Retail Pharmacy International
Disaggregation of Revenue [Line Items]
Sales	2,745	2,901
Reportable Segments | Retail Pharmacy International | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	1,001	1,039
Reportable Segments | Retail Pharmacy International | Retail
Disaggregation of Revenue [Line Items]
Sales	1,744	1,862
Reportable Segments | Pharmaceutical Wholesale
Disaggregation of Revenue [Line Items]
Sales	6,007	5,708
Eliminations
Disaggregation of Revenue [Line Items]
Sales	$ (545)	$ (537)