Retirement benefits - Schedule of Net Periodic Pension Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2025	May 31, 2024	May 31, 2025	May 31, 2024
Retirement Benefits [Abstract]
Service costs	$ 1	$ 1	$ 2	$ 3
Interest costs	63	68	187	202
Expected returns on plan assets/other	(62)	(70)	(185)	(206)
Total net periodic pension cost (income)	$ 2	$ (1)	$ 5	$ (1)