Debt - short-term borrowings (Details) - USD ($) $ in Millions	Aug. 31, 2019	Aug. 31, 2018
Short-Term Borrowings [Abstract]
Total short-term debt	$ 5,738	$ 1,966
Other Short Term Debt
Short-Term Borrowings [Abstract]
Total short-term debt	464	288
Commercial Paper
Short-Term Borrowings [Abstract]
Total short-term debt	2,400	430
Credit facilities
Short-Term Borrowings [Abstract]
Total short-term debt	1,624	999
Notes Payable | 2.700% unsecured notes due 2019
Short-Term Borrowings [Abstract]
Total short-term debt	$ 1,250	0
Stated interest rate (as a percent)	2.70%
Notes Payable | 5.250% unsecured notes due 2019
Short-Term Borrowings [Abstract]
Total short-term debt	$ 0	$ 249
Stated interest rate (as a percent)	5.25%