Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 35,820	$ 34,528	$ 70,160	$ 68,321
Reportable Segments | Retail Pharmacy USA
Disaggregation of Revenue [Line Items]
Sales	27,245	26,257	53,377	51,979
Reportable Segments | Retail Pharmacy USA | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	19,901	18,892	39,606	38,039
Reportable Segments | Retail Pharmacy USA | Retail
Disaggregation of Revenue [Line Items]
Sales	7,344	7,366	13,772	13,940
Reportable Segments | Retail Pharmacy International
Disaggregation of Revenue [Line Items]
Sales	3,056	3,082	5,801	5,982
Reportable Segments | Retail Pharmacy International | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	1,025	1,010	2,026	2,049
Reportable Segments | Retail Pharmacy International | Retail
Disaggregation of Revenue [Line Items]
Sales	2,031	2,072	3,775	3,933
Reportable Segments | Pharmaceutical Wholesale
Disaggregation of Revenue [Line Items]
Sales	6,066	5,738	12,072	11,446
Eliminations
Disaggregation of Revenue [Line Items]
Sales	$ (546)	$ (549)	$ (1,091)	$ (1,086)