Supplemental information - Depreciation and Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
Supplemental Cash Flow Elements [Abstract]
Depreciation expense	$ 365	$ 379	$ 1,099	$ 1,096
Intangible asset and other amortization	112	142	348	415
Total depreciation and amortization expense	$ 477	$ 522	$ 1,447	$ 1,512