Related parties (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Related Party Transactions [Abstract]
Purchases, net	$ 12,132	$ 10,602	$ 23,736	$ 21,238
Trade accounts payable, net	$ 5,488	$ 4,384	$ 5,488	$ 4,384