Income tax - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2024	Jul. 31, 2023	Jul. 31, 2022
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of fiscal year	$ 144	$ 140	$ 132
Additions based on tax positions related to current year	25	27	27
Additions for tax positions of prior years	2	2	11
Reductions for tax positions of prior years	(10)	0	0
Reductions due to lapse of statute of limitations	(10)	(25)	(30)
Unrecognized tax benefits	$ 151	$ 144	$ 140