Retirement benefits - components of net periodic pension costs (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income, net	Other income, net	Other income, net
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income, net	Other income, net	Other income, net
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs (Selling, general and administrative expenses)	$ 4	$ 5	$ 6
Interest costs (Other income, net)	264	149	139
Expected returns on plan assets/other (Other income, net)	(340)	(280)	(332)
Total net periodic pension income	$ (72)	$ (126)	$ (188)