Goodwill and other intangible assets - Narrative (Details) $ in Millions	3 Months Ended				9 Months Ended
	May 31, 2025 USD ($)	Feb. 28, 2025 USD ($)	May 31, 2024 USD ($)	Feb. 29, 2024 USD ($) clinic	May 31, 2025 USD ($)	May 31, 2024 USD ($) clinic
Goodwill [Line Items]
Impairment of goodwill	$ 0		$ 0		$ 3,653	$ 12,369
Impairment				$ 266
Impairment of goodwill, intangibles and long-lived assets					$ 5,776	$ 13,618
U.S. Healthcare
Goodwill [Line Items]
Impairment of goodwill		$ 178
U.S. Retail Pharmacy
Goodwill [Line Items]
Impairment of goodwill		2,000
Transformational Cost Management Program
Goodwill [Line Items]
Number of clinics closed | clinic				90		160
VillageMD
Goodwill [Line Items]
Impairment of goodwill		1,500		$ 12,400
Impairment		1,600
Impairment of goodwill, intangibles and long-lived assets		3,000
Asset impairment charges, net of controlling interest		1,900
U.S. Retail Pharmacy, CareCentrix, and Boots
Goodwill [Line Items]
Impairment of goodwill, intangibles and long-lived assets		2,300
Boots | International
Goodwill [Line Items]
Impairment of intangible assets (excluding goodwill)		$ 115