Debt - Short and Long-Term Debt (Details) - USD ($) $ in Millions	Feb. 29, 2020	Aug. 31, 2019
Debt Instrument [Line Items]
Total short-term debt	$ 5,984	$ 5,738
Total long-term debt, less current portion	10,625	11,098
Unsecured Notes
Debt Instrument [Line Items]
Other	24	25
Total long-term debt, less current portion	10,625	11,098
Unsecured Notes | 2.875% unsecured Pound sterling notes due 2020
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 0	488
Stated interest rate	2.875%
Unsecured Notes | 3.450% unsecured notes due 2026
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 1,890	1,890
Stated interest rate	3.45%
Unsecured Notes | 4.650% unsecured notes due 2046
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 591	591
Stated interest rate	4.65%
Unsecured Notes | 3.300% unsecured notes due 2021
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 1,247	1,247
Stated interest rate	3.30%
Unsecured Notes | 3.800% unsecured notes due 2024
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 1,992	1,992
Stated interest rate	3.80%
Unsecured Notes | 4.500% unsecured notes due 2034
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 496	495
Stated interest rate	4.50%
Unsecured Notes | 4.800% unsecured notes due 2044
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 1,493	1,492
Stated interest rate	4.80%
Unsecured Notes | 3.600% unsecured Pound sterling notes due 2025
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 384	365
Stated interest rate	3.60%
Unsecured Notes | 2.125% unsecured Euro notes due 2026
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 818	824
Stated interest rate	2.125%
Unsecured Notes | 3.100% unsecured notes due 2022
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 1,197	1,197
Stated interest rate	3.10%
Unsecured Notes | 4.400% unsecured notes due 2042
Debt Instrument [Line Items]
Carrying value of notes, net of unamortized discount and interest rate swap FMV adjustment	$ 493	493
Stated interest rate	4.40%
Commercial Paper
Debt Instrument [Line Items]
Total short-term debt	$ 2,517	2,400
Credit facilities
Debt Instrument [Line Items]
Total short-term debt	2,512	1,624
Notes payable to banks | 2.700% unsecured notes due 2019
Debt Instrument [Line Items]
Total short-term debt	$ 0	1,250
Stated interest rate	2.70%
Notes payable to banks | 2.875% unsecured Pound sterling notes due 2020
Debt Instrument [Line Items]
Total short-term debt	$ 513	0
Other
Debt Instrument [Line Items]
Total short-term debt	$ 443	$ 464