Goodwill and other intangible assets - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 29, 2024 USD ($) clinic	Feb. 28, 2023 USD ($)	Feb. 29, 2024 USD ($)	Feb. 28, 2023 USD ($)
Goodwill [Line Items]
Impairments	$ 12,369	$ 0	$ 12,369	$ 0
Asset impairment charges			266
Amortization of intangible assets	$ 239	$ 199	$ 478	$ 357
Transformational Cost Management Program
Goodwill [Line Items]
Number of clinics closed | clinic	90
U.S. Healthcare
Goodwill [Line Items]
Impairments	$ 12,400