Income taxes - narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021	Aug. 31, 2020
Operating Loss Carryforwards [Line Items]
Effective income tax rate	34.30%	(0.80%)	33.40%
Deferred tax assets, tax attributes	$ 7,784	$ 7,825
Income tax credits	158
Deferred tax assets operating loss carryforwards subject to expiration	6,900
Deferred tax assets operating loss carryforwards not subject to expiration	832
Valuation allowance	7,360	7,521
Income taxes paid	64	387	$ 336
Unrecognized tax benefits	1,106	1,110	1,098	$ 494
Unrecognized tax benefits reported against deferred taxes	413	473
Unrecognized tax benefits reported against tax receivables	116	116
Unrecognized tax benefits would favorably impact the effective tax rate if recognized	588	529	524
Decrease in unrecognized tax benefits is reasonably possible	257
Accrued interest and penalties in income tax provision	125	97
Interest and penalties included in income tax expense	29	13	26
Unrecorded deferred tax liability for temporary differences related to foreign subsidiaries	9	104	118
Tax cuts and jobs act, measurement period adjustment, income tax expense (benefit)			(247)
Long-term liabilities
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	703	$ 618
U.S. Federal
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards	1,800
State
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards	465
Non-U.S.
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards	$ 28,700
United Kingdom
Operating Loss Carryforwards [Line Items]
Tax expense recorded from re-measurement of foreign deferred tax liabilities from changes in tax laws			$ 344