Retirement benefits - components of net periodic pension costs (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs (Selling, general and administrative expenses)	$ 6	$ 2	$ 2
Interest costs (Other income)	139	141	195
Expected returns on plan assets/other (Other income)	(332)	(285)	(245)
Total net periodic pension (income) cost	$ (188)	$ (142)	$ (48)