Income taxes - additional information (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 01, 2020	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Operating Loss Carryforwards [Line Items]
U.S. statutory federal tax rate		21.00%	21.00%	25.70%
Tax Cuts and Jobs Act Of 2017, discrete tax provision			$ 89
Tax Cuts And Jobs Act Of 2017, income tax benefit				$ 125
Tax Cuts and Jobs Act, provisional income tax benefit due to remeasurement of deferred tax liabilities				648
Transition tax, provisional discrete tax expense				523
Tax Cuts and Jobs Act, measurement period adjustment, income tax benefit			247
Tax attributes		$ 6,909	6,687
Income tax credits		71
Deferred tax assets operating loss carryforwards subject to expiration		6,200
Deferred tax assets operating loss carryforwards not subject to expiration		692
Valuation allowance		6,608	6,638
Income taxes paid		600	900	600
Unrecognized tax benefits		494	455	456	$ 409
Unrecognized tax benefits would favorably impact the effective tax rate if recognized		353	311	$ 331
Decrease in unrecognized tax benefits is reasonably possible		2
Accrued interest and penalties in income tax provision		58	47
Interest and penalties included in income tax expense		11
Unrecorded deferred tax liability for temporary differences related to foreign subsidiaries		124	$ 127
United Kingdom
Operating Loss Carryforwards [Line Items]
Tax expense recorded from re-measurement of foreign deferred tax liabilities from changes in tax laws	$ 139
U.S. Federal
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards		2,900
State
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards		276
Non-U.S.
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards		24,100
Long-term liabilities
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits		$ 552