Assets and liabilities at fair value - Schedule of Debt Measured at Fair Value (Details) - Level 2 - USD ($) $ in Millions	Apr. 30, 2025	Jul. 31, 2024
Unsecured senior notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	$ 3,079	$ 2,333
Fair Value	3,006	2,263
Private placement notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	700	849
Fair Value	$ 698	$ 837