Retirement benefits - Schedule of Net Periodic Pension Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2025	Feb. 29, 2024	Feb. 28, 2025	Feb. 29, 2024
Retirement Benefits [Abstract]
Service costs	$ (1)
Service costs		$ 1	$ 2	$ 2
Interest costs	61	64	124	134
Expected returns on plan assets/other	(60)	(63)	(122)	(136)
Total net periodic pension cost	$ 0	$ 3	$ 3	$ 0