Sales (Details) - USD ($) $ in Millions	3 Months Ended
	Nov. 30, 2018	Nov. 30, 2017
Disaggregation of Revenue [Line Items]
Sales	$ 33,793	$ 30,740
Reportable Segments | Retail Pharmacy USA
Disaggregation of Revenue [Line Items]
Sales	25,721	22,489
Reportable Segments | Retail Pharmacy USA | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	19,147	16,282
Reportable Segments | Retail Pharmacy USA | Retail
Disaggregation of Revenue [Line Items]
Sales	6,574	6,207
Reportable Segments | Retail Pharmacy International
Disaggregation of Revenue [Line Items]
Sales	2,901	3,083
Reportable Segments | Retail Pharmacy International | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	1,039	1,104
Reportable Segments | Retail Pharmacy International | Retail
Disaggregation of Revenue [Line Items]
Sales	1,862	1,979
Reportable Segments | Pharmaceutical Wholesale
Disaggregation of Revenue [Line Items]
Sales	5,708	5,718
Eliminations
Disaggregation of Revenue [Line Items]
Sales	$ (537)	$ (550)