Retirement benefits - narrative (Details) $ in Millions			12 Months Ended
	Dec. 07, 2023 USD ($)	Nov. 23, 2023 USD ($) member	Aug. 31, 2024 USD ($)	Aug. 31, 2023 USD ($)	Aug. 31, 2022 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Accelerated future employer contributions		$ 210
Contributions by employer	$ 375
Plan assets, period increase			$ 124
Annuity			6,000
Annuity deferred premiums			860
Annuity payments			229
Reduction in benefit obligation due to potential discount rate decrease			149
Reduction in benefit obligation due to potential expected return decrease			15
Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions		760
Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions		$ 820
Postretirement Health Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan obligation			114	$ 113
Expected benefit to be paid next fiscal year			7
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Number of members | member		53,000
Contributions by employer			435	40
Defined benefit plan obligation			5,433	5,515	$ 5,967
Expected benefit to be paid next fiscal year			312
United States
Defined Benefit Plan Disclosure [Line Items]
Profit sharing provision expense			223	239	234
Contributions to profit sharing			223	241	236
Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Cost recognized in the consolidated condensed statements of earnings			$ 101	$ 83	$ 90