Retirement benefits - changes in benefit obligations (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	$ 5,967	$ 10,206
Service costs	4	5	$ 6
Interest costs	264	149	139
Net actuarial gain	(897)	(3,042)
Benefits paid	(286)	(304)
Currency translation adjustments	463	(1,047)
Benefit obligation at end of year	$ 5,515	$ 5,967	$ 10,206