Retirement benefit obligations - OCI (Details) - USD ($) $ in Millions	12 Months Ended
Jul. 31, 2025	Jul. 31, 2024	Jul. 31, 2023
Retirement Benefits [Abstract]
Net actuarial loss (gain)	$ 69	$ 31	$ 83
Amortization of net actuarial loss	(15)	(15)	(11)
Impact of exchange rates	(4)	(1)	(7)
Income tax impact	(12)	(4)	(16)
Other comprehensive loss, net of tax	$ 38	$ 11	$ 49

Other Comprehensive Income (Loss), Defined Benefit Plan, Amortization Of Loss

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Other Comprehensive Income (Loss), Defined Benefit Plan, Foreign Currency Transaction And Translation Adjustment, after Tax

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Other Comprehensive Income (Loss), Defined Benefit Plan, Tax

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Amount, after tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

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