Goodwill and other intangible assets - Narrative (Details) $ in Millions	3 Months Ended			9 Months Ended
	May 31, 2024 USD ($)	Feb. 29, 2024 USD ($) clinic	May 31, 2023 USD ($)	May 31, 2024 USD ($)	May 31, 2023 USD ($)
Goodwill [Line Items]
Impairments	$ 0		$ 0	$ 12,369	$ 0
Amortization of intangible assets	238		$ 226	$ 717	$ 583
Transformational Cost Management Program
Goodwill [Line Items]
Number of clinics closed | clinic		90
U.S. Healthcare
Goodwill [Line Items]
Impairments		$ 12,400
Asset impairment charges		$ 266
International
Goodwill [Line Items]
Impairments	$ 431