Accumulated other comprehensive loss - Schedule of Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2025	Oct. 31, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax benefit	$ 142	$ 154
Amounts reclassified from accumulated other comprehensive loss	(570)	(470)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses	4	4
Tax benefit	(1)	(1)
Amounts reclassified from accumulated other comprehensive loss	$ 3	$ 3