Fair value measurements - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2024	Jul. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Hedged Liability Statement Of Financial Position Extensible Enumeration Not Disclosed Flag	fair value hedges	fair value hedges
Hedged liability, fair value hedge	$ 300	$ 355
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of equity investments	$ 28	$ 34