Supplemental information - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	May 31, 2019	May 31, 2018	Aug. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable from related party		$ 1,300	$ 1,200
Restricted cash (included in other current assets)	$ 199		190
Antidilutive securities excluded from EPS calculations (in shares)	17.0	12.1
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade receivables		$ 5,900	$ 5,400