Supplemental information - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Aug. 31, 2018
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	10,600		10,500
Restricted cash (included in other current assets)	$ 203		190
Antidilutive securities excluded from EPS calculations (in shares)	11.3	7.6
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables	$ 5,900		$ 5,400