Supplemental information - Depreciation and Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2018	May 31, 2017	Aug. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 358	$ 334	$ 1,040	$ 1,000
Intangible asset and other amortization	84	79	260	244
Total depreciation and amortization expense	442	$ 413	1,300	$ 1,244
Accumulated depreciation and amortization on property, plant, and equipment	$ 10,200		$ 10,200		$ 9,300