Assets and liabilities at fair value -Debt Measured at Fair Value (Details) - Level 2 - USD ($) $ in Millions	Jan. 31, 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	2,973	2,263
Private placement notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	700	849
Fair Value	$ 694	$ 837