Leases - supplemental balance sheet information (Details) - USD ($) $ in Millions	Aug. 31, 2021	Aug. 31, 2020
Operating Leases:
Operating lease right-of-use assets	$ 21,893	$ 21,453
Operating lease obligations - current	2,259	2,358
Operating lease obligations - non current	22,153	21,765
Total operating lease obligations	24,412	24,123
Finance Leases:
Property, plant and equipment, net	725	766
Lease obligations included in:
Accrued expenses and other liabilities	37	31
Other non-current liabilities	974	1,013
Total finance lease obligations	$ 1,010	$ 1,044
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization	Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other non-current liabilities	Other non-current liabilities