Retirement benefits - accumulated other comprehensive income (Details) - Pension Plan - USD ($) $ in Millions	Aug. 31, 2024	Aug. 31, 2023	Aug. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 262	$ 730	$ (251)
Prior service cost	(273)	(1)	(1)
Total pre-tax comprehensive loss (income)	$ (11)	$ 729	$ (252)

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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