Sales (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Disaggregation of Revenue [Line Items]
Sales	$ 33,954	$ 34,591	$ 34,528	$ 33,793	$ 33,442	$ 34,334	$ 33,021	$ 30,740	$ 136,866	$ 131,537	$ 118,214
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Sales									(2,180)	(2,142)	(2,089)
Retail Pharmacy USA | Operating Segments
Disaggregation of Revenue [Line Items]
Sales									104,532	98,392	87,302
Retail Pharmacy USA | Operating Segments | Pharmacy
Disaggregation of Revenue [Line Items]
Sales									77,192	71,055	60,608
Retail Pharmacy USA | Operating Segments | Retail
Disaggregation of Revenue [Line Items]
Sales									27,340	27,337	26,695
Retail Pharmacy International | Operating Segments
Disaggregation of Revenue [Line Items]
Sales									11,462	12,281	11,813
Retail Pharmacy International | Operating Segments | Pharmacy
Disaggregation of Revenue [Line Items]
Sales									4,080	4,360	4,180
Retail Pharmacy International | Operating Segments | Retail
Disaggregation of Revenue [Line Items]
Sales									7,382	7,921	7,633
Pharmaceutical Wholesale | Operating Segments
Disaggregation of Revenue [Line Items]
Sales									$ 23,053	$ 23,006	$ 21,188