Goodwill and other intangible assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2025	Feb. 29, 2024	Feb. 28, 2025	Feb. 29, 2024	Aug. 31, 2024
Goodwill [Roll Forward]
Goodwill, beginning balance			$ 15,506
Impairments	$ (3,653)	$ (12,369)	(3,653)	$ (12,369)
Cumulative translation adjustments			(51)
Goodwill, ending balance	11,803		11,803
U.S. Retail Pharmacy
Goodwill [Roll Forward]
Impairments	(2,000)
U.S. Healthcare
Goodwill [Roll Forward]
Impairments	(178)
Reportable Segments | U.S. Retail Pharmacy
Goodwill [Roll Forward]
Goodwill, beginning balance			10,947
Impairments			(2,008)
Cumulative translation adjustments			0
Goodwill, ending balance	8,938		8,938
Goodwill, impaired, accumulated impairment loss					$ 0
Reportable Segments | International
Goodwill [Roll Forward]
Goodwill, beginning balance			1,388
Impairments			0
Cumulative translation adjustments			(51)
Goodwill, ending balance	1,337		1,337
Goodwill, impaired, accumulated impairment loss					1,700
Reportable Segments | U.S. Healthcare
Goodwill [Roll Forward]
Goodwill, beginning balance			3,173
Impairments			(1,645)
Cumulative translation adjustments			0
Goodwill, ending balance	$ 1,528		$ 1,528
Goodwill, impaired, accumulated impairment loss					$ 12,700