Retirement benefits - Schedule of Net Periodic Pension Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 29, 2024	Feb. 28, 2023	Feb. 29, 2024	Feb. 28, 2023
Retirement Benefits [Abstract]
Service costs	$ 1	$ 1	$ 2	$ 2
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]		Other income (expense), net		Other income (expense), net
Interest costs	64	$ 63	134	$ 122
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Other income (expense), net		Other income (expense), net
Expected returns on plan assets/other	(63)	$ (80)	(136)	$ (156)
Total net periodic pension expense (income)	$ 3	$ (16)	$ 0	$ (32)