Goodwill and other intangible assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 29, 2024	Feb. 28, 2023	Feb. 29, 2024	Feb. 28, 2023
Goodwill [Roll Forward]
Goodwill, beginning balance			$ 28,187
Adjustments			22
Impairments	$ (12,369)	$ 0	(12,369)	$ 0
Cumulative translation adjustments and other			(26)
Goodwill, ending balance	15,814		15,814
U.S. Healthcare
Goodwill [Roll Forward]
Impairments	(12,400)
Reportable Segments | U.S. Retail Pharmacy
Goodwill [Roll Forward]
Goodwill, beginning balance			10,947
Adjustments			0
Impairments			0
Cumulative translation adjustments and other			0
Goodwill, ending balance	10,947		10,947
Reportable Segments | International
Goodwill [Roll Forward]
Goodwill, beginning balance			1,378
Adjustments			0
Impairments			0
Cumulative translation adjustments and other			(18)
Goodwill, ending balance	1,360		1,360
Reportable Segments | U.S. Healthcare
Goodwill [Roll Forward]
Goodwill, beginning balance			15,863
Adjustments			22
Impairments			(12,369)
Cumulative translation adjustments and other			(8)
Goodwill, ending balance	$ 3,508		$ 3,508