Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Aug. 31, 2020	May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 34,746	$ 34,631	$ 35,820	$ 34,339	$ 33,954	$ 34,591	$ 34,528	$ 33,793	$ 139,537	$ 136,866	$ 131,537
Eliminations
Disaggregation of Revenue [Line Items]
Sales									(2,126)	(2,180)	(2,142)
Retail Pharmacy USA | Reportable Segments
Disaggregation of Revenue [Line Items]
Sales									107,701	104,532	98,392
Retail Pharmacy USA | Reportable Segments | Pharmacy
Disaggregation of Revenue [Line Items]
Sales									80,481	77,192	71,055
Retail Pharmacy USA | Reportable Segments | Retail
Disaggregation of Revenue [Line Items]
Sales									27,220	27,340	27,337
Retail Pharmacy International | Reportable Segments
Disaggregation of Revenue [Line Items]
Sales									10,004	11,462	12,281
Retail Pharmacy International | Reportable Segments | Pharmacy
Disaggregation of Revenue [Line Items]
Sales									3,906	4,080	4,360
Retail Pharmacy International | Reportable Segments | Retail
Disaggregation of Revenue [Line Items]
Sales									6,098	7,382	7,921
Pharmaceutical Wholesale | Reportable Segments
Disaggregation of Revenue [Line Items]
Sales									$ 23,958	$ 23,053	$ 23,006