Supplemental information - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Aug. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable from related party	$ 1,300		$ 1,200
Accumulated depreciation and amortization on property, plant, and equipment	11,600		11,300
Restricted cash (included in other current assets)	$ 189		184
Antidilutive securities excluded from EPS calculations (in shares)	16.7	11.3
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 6,100		$ 6,000