Retirement benefit obligations - Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2024	Jul. 31, 2023	Jul. 31, 2022
Change in net benefit obligations:
Beginning balance	$ 1,218	$ 1,402
Interest cost	62	51	$ 41
Actuarial loss (gain)	36	(245)
Benefits paid	(63)	(57)
Exchange rate adjustment	(2)	67
Ending balance	1,251	1,218	1,402
Change in assets at fair value:
Beginning balance	1,270	1,508
Actual return on plan assets	68	(279)
Company contributions	34	24
Benefits paid	(63)	(57)
Exchange rate adjustment	(1)	74
Ending balance at fair value	1,308	1,270	$ 1,508
Funded status of plans	$ 57	$ 52