Accumulated other comprehensive loss - Schedule of Reclassification Out of AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2025	Jul. 31, 2024	Jul. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax benefit	$ 567	$ 729	$ 575
Amounts reclassified from accumulated other comprehensive loss	(1,856)	(1,735)	(1,889)
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	15	15	11
Tax benefit	(4)	(4)	(3)
Amounts reclassified from accumulated other comprehensive loss	$ 11	$ 11	$ 8