Income taxes - narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2022	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Operating Loss Carryforwards [Line Items]
Tax cuts and jobs act, measurement period adjustment, income tax expense (benefit)			$ (247)
Effective income tax rate	(0.80%)	33.40%	76.00%
Deferred tax assets, tax attributes	$ 7,825	$ 7,467
Income tax credits	91
Deferred tax assets operating loss carryforwards subject to expiration	7,300
Deferred tax assets operating loss carryforwards not subject to expiration	483
Valuation allowance	7,521	7,239
Income taxes paid	387	336	$ 626
Unrecognized tax benefits	1,110	1,098	494	$ 455
Unrecognized tax benefits reported against deferred taxes	473	475
Unrecognized tax benefits reported against tax receivables	116	114
Unrecognized tax benefits would favorably impact the effective tax rate if recognized	529	524	353
Decrease in unrecognized tax benefits is reasonably possible	136
Accrued interest and penalties in income tax provision	97	84
Interest and penalties included in income tax expense	13	26	11
Unrecorded deferred tax liability for temporary differences related to foreign subsidiaries	104	118	$ 124
Long-term liabilities
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	618	594
U.S. Federal
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards	1,600
State
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards	153
Non-U.S.
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards	28,800
United Kingdom
Operating Loss Carryforwards [Line Items]
Tax expense recorded from re-measurement of foreign deferred tax liabilities from changes in tax laws	$ 344	$ 139