Leases - supplemental cash flow information (Details) $ in Millions	12 Months Ended
	Aug. 31, 2020 USD ($)
Cash paid for amounts included in the measurement of lease obligations
Operating cash flows from operating leases	$ 3,315
Operating cash flows from finance leases	48
Financing cash flows from finance leases	51
Total	3,414
Right-of-use assets obtained in exchange for new lease obligations:
Operating leases	2,494
Finance leases	65
Total	$ 2,559