Retirement benefits - Schedule of Net Periodic Pension Income (Details) - USD ($) $ in Millions	3 Months Ended
	Nov. 30, 2023	Nov. 30, 2022
Components of net periodic benefit costs [Abstract]
Service costs	$ 1	$ 1
Interest costs	70	59
Expected returns on plan assets/other	(73)	(75)
Total net periodic pension income	(3)	(15)
U.S. Retail Pharmacy
Components of net periodic benefit costs [Abstract]
Profit sharing provision expense	60	65
Foreign Plan
Components of net periodic benefit costs [Abstract]
Cost recognized in the consolidated condensed statements of earnings	$ 22	$ 20