Sales (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Disaggregation of Revenue [Line Items]
Sales	$ 32,779	$ 31,336	$ 64,217	$ 61,247
Reportable Segments | United States
Disaggregation of Revenue [Line Items]
Sales	27,344	27,245	54,507	53,377
Reportable Segments | United States | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	20,494	19,901	41,363	39,606
Reportable Segments | United States | Retail
Disaggregation of Revenue [Line Items]
Sales	6,850	7,344	13,144	13,772
Reportable Segments | International
Disaggregation of Revenue [Line Items]
Sales	5,425	4,091	9,709	7,870
Reportable Segments | International | Pharmacy
Disaggregation of Revenue [Line Items]
Sales	938	923	1,833	1,821
Reportable Segments | International | Retail
Disaggregation of Revenue [Line Items]
Sales	1,632	1,981	3,154	3,677
Reportable Segments | International | Wholesale
Disaggregation of Revenue [Line Items]
Sales	2,855	1,187	4,722	2,372
Corporate and Other
Disaggregation of Revenue [Line Items]
Sales	$ 10	$ 0	$ 0	$ 0