Income tax - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jul. 31, 2024	Jul. 31, 2024	Jul. 31, 2023	Jul. 31, 2022	Jul. 31, 2021
Investments, Owned, Federal Income Tax Note [Line Items]
Change in valuation allowance	$ 47	$ 47	$ 4	$ 0
U.K. federal operating loss carryforwards	343	343
Unrecognized tax benefits	151	151	144	140	$ 132
Accrued interest	28	28	23	17
Interest included in income tax expense (benefit)		5	6	$ 1
Decrease in unrecognized tax benefits is reasonably possible	37	37
Foreign earnings reinvested	795	795	$ 725
Foreign, United States
Investments, Owned, Federal Income Tax Note [Line Items]
Foreign gross loss carryforwards	11	11
U.S. state operating loss carryforwards	12	12
Foreign, Excluding United States
Investments, Owned, Federal Income Tax Note [Line Items]
Foreign gross loss carryforwards	$ 8	$ 8